<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:6da65d26-0527-464c-9636-2c9ac97f0eeb,g:6a05fa62-e6fd-49ca-b27d-73c0b4dbf900-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://opendoor.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="open-20230630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="idcb122dca6c44f12b48ddf19a06c0537_CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_fe1f3c55-c12c-467d-bb2e-ee775e5c5871" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_fe1f3c55-c12c-467d-bb2e-ee775e5c5871" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_0c5e9a72-d496-4b2b-8e84-9229ebe02cc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_0c5e9a72-d496-4b2b-8e84-9229ebe02cc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRealEstate_7faa3043-66bf-4e0e-9968-85d64b64ec2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_InventoryRealEstate_7faa3043-66bf-4e0e-9968-85d64b64ec2d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EscrowDeposit_a3c9b03c-94e1-4f79-8658-83e49ec1bf22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EscrowDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_EscrowDeposit_a3c9b03c-94e1-4f79-8658-83e49ec1bf22" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_31cf4a79-8934-4acc-a1bc-df7037375b65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_OtherAssetsCurrent_31cf4a79-8934-4acc-a1bc-df7037375b65" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_0a6d3f34-010d-44c0-903e-ea0a13c097f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_Assets_0a6d3f34-010d-44c0-903e-ea0a13c097f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent_6a1be672-e712-4ff1-9cdd-bbd162e9de14" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent_6a1be672-e712-4ff1-9cdd-bbd162e9de14" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrent_2c18d172-da31-4542-9c96-f436a4f68d79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_InterestPayableCurrent_2c18d172-da31-4542-9c96-f436a4f68d79" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditCurrent_69218681-d6ee-4000-9c9e-5eea2ad86b36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LinesOfCreditCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_LinesOfCreditCurrent_69218681-d6ee-4000-9c9e-5eea2ad86b36" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermLineOfCredit_c931a4f4-8e17-4265-88a0-fb8e3bf93de9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermLineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_LongTermLineOfCredit_c931a4f4-8e17-4265-88a0-fb8e3bf93de9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_7b1193ed-8c9a-4c08-b13e-f911644c9ccf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_Liabilities_7b1193ed-8c9a-4c08-b13e-f911644c9ccf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_4c2a4b5b-db6f-4d61-a676-9efde16b4e56" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ad3030eb-ce6e-49aa-8df3-0a9ddeb1ce47" xlink:to="loc_us-gaap_StatementTable_4c2a4b5b-db6f-4d61-a676-9efde16b4e56" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_0fc795a7-7a51-4035-a547-e01e5457e31f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_4c2a4b5b-db6f-4d61-a676-9efde16b4e56" xlink:to="loc_srt_ConsolidatedEntitiesAxis_0fc795a7-7a51-4035-a547-e01e5457e31f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0fc795a7-7a51-4035-a547-e01e5457e31f_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_0fc795a7-7a51-4035-a547-e01e5457e31f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0fc795a7-7a51-4035-a547-e01e5457e31f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_67293dd1-d74b-4336-899e-1a5ae0e795b0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_0fc795a7-7a51-4035-a547-e01e5457e31f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_67293dd1-d74b-4336-899e-1a5ae0e795b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_4d5e6a03-ab01-45fc-9426-5315518e2672" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_67293dd1-d74b-4336-899e-1a5ae0e795b0" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_4d5e6a03-ab01-45fc-9426-5315518e2672" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY" xlink:type="simple" xlink:href="open-20230630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY" xlink:type="extended" id="id6a5eb0ab89746669b025345a104d807_CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d9760b03-6ab3-4d1b-a1f3-e31a1d854b15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d9760b03-6ab3-4d1b-a1f3-e31a1d854b15" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_e861ce8c-ae22-4985-a16f-d70c8661cea8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_e861ce8c-ae22-4985-a16f-d70c8661cea8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_2fcf69f2-d44f-49c5-a2aa-a2db341dd0f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockholdersEquity_2fcf69f2-d44f-49c5-a2aa-a2db341dd0f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_f14a4a18-4118-466b-b7ec-ec9271faf1b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_f14a4a18-4118-466b-b7ec-ec9271faf1b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3c9b7407-7731-46f4-a309-3a6fc262d09e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3c9b7407-7731-46f4-a309-3a6fc262d09e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_38b01b67-3b73-47ca-9778-1f0b3eed4505" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_38b01b67-3b73-47ca-9778-1f0b3eed4505" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_380fde9f-0688-4b83-b104-b52e8ffbd752" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_380fde9f-0688-4b83-b104-b52e8ffbd752" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_10648109-c90b-4f96-8ba3-8078e01c30ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_10648109-c90b-4f96-8ba3-8078e01c30ca" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4ea0c7af-9173-4d8b-b8cd-660d6d83b912" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4ea0c7af-9173-4d8b-b8cd-660d6d83b912" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_f2c87357-7cc5-45cd-ac18-e7794e70f54a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_f2c87357-7cc5-45cd-ac18-e7794e70f54a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_8872f597-24f8-45ee-95c3-35c78d99f0b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f0734cac-6b8f-413b-ba4e-25370a77307a" xlink:to="loc_us-gaap_NetIncomeLoss_8872f597-24f8-45ee-95c3-35c78d99f0b9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_dadea0c7-f2f4-43ed-bea9-ce5718f33c7a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_40e59c82-1a55-4517-99cc-1f08366d9f3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f52760eb-d809-410a-b655-0955e21ab7d0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_d9760b03-6ab3-4d1b-a1f3-e31a1d854b15" xlink:to="loc_us-gaap_StatementTable_f52760eb-d809-410a-b655-0955e21ab7d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f52760eb-d809-410a-b655-0955e21ab7d0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5" xlink:to="loc_us-gaap_EquityComponentDomain_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e4d50a9b-6ab2-43b4-ba99-e6744cbd51f5" xlink:to="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_a9ea9b76-a2d9-4e0a-9e78-c9e7e0fd6ed2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:to="loc_us-gaap_CommonStockMember_a9ea9b76-a2d9-4e0a-9e78-c9e7e0fd6ed2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_b9be1ca3-8a51-4ba8-ace0-c97b6e2f7a11" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_b9be1ca3-8a51-4ba8-ace0-c97b6e2f7a11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_83b9319b-4680-4214-b2ae-4c73eb0d393c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:to="loc_us-gaap_RetainedEarningsMember_83b9319b-4680-4214-b2ae-4c73eb0d393c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_a2d84fa9-30c8-4b48-9f7a-e03abd51d540" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ac144699-cfe8-4f4d-a96f-0cd991e36075" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_a2d84fa9-30c8-4b48-9f7a-e03abd51d540" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_26fc4793-94d7-42e6-874d-4a688f3f2646" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f52760eb-d809-410a-b655-0955e21ab7d0" xlink:to="loc_us-gaap_AwardTypeAxis_26fc4793-94d7-42e6-874d-4a688f3f2646" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_26fc4793-94d7-42e6-874d-4a688f3f2646_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_26fc4793-94d7-42e6-874d-4a688f3f2646" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_26fc4793-94d7-42e6-874d-4a688f3f2646_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_014c2d26-65f8-466f-9230-ca30395cbac7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_26fc4793-94d7-42e6-874d-4a688f3f2646" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_014c2d26-65f8-466f-9230-ca30395cbac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_7fee6a86-dcb3-42d8-90cc-3245adc46de1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_014c2d26-65f8-466f-9230-ca30395cbac7" xlink:to="loc_us-gaap_RestrictedStockMember_7fee6a86-dcb3-42d8-90cc-3245adc46de1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_97a60638-6ac3-441d-8ea9-0846d60e0d9c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_014c2d26-65f8-466f-9230-ca30395cbac7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_97a60638-6ac3-441d-8ea9-0846d60e0d9c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/DESCRIPTIONOFBUSINESSANDACCOUNTINGPOLICIESConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#DESCRIPTIONOFBUSINESSANDACCOUNTINGPOLICIESConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/DESCRIPTIONOFBUSINESSANDACCOUNTINGPOLICIESConvertibleSeniorNotesDetails" xlink:type="extended" id="ic568b35bf7c24cc1aafa14aa6eb5d736_DESCRIPTIONOFBUSINESSANDACCOUNTINGPOLICIESConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_e25a3eaf-d998-42c8-8621-a3501e71467d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3801baac-c946-4c5c-af7c-42d7865502a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e25a3eaf-d998-42c8-8621-a3501e71467d" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3801baac-c946-4c5c-af7c-42d7865502a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ed37e808-c38d-4a0f-9d77-433c052a15be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e25a3eaf-d998-42c8-8621-a3501e71467d" xlink:to="loc_us-gaap_DebtInstrumentTable_ed37e808-c38d-4a0f-9d77-433c052a15be" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_5d43276a-1789-49ba-81b6-d645f574ba04" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ed37e808-c38d-4a0f-9d77-433c052a15be" xlink:to="loc_us-gaap_DebtInstrumentAxis_5d43276a-1789-49ba-81b6-d645f574ba04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5d43276a-1789-49ba-81b6-d645f574ba04_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_5d43276a-1789-49ba-81b6-d645f574ba04" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5d43276a-1789-49ba-81b6-d645f574ba04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_84f05f50-eb11-4cec-8c84-ae11a54c253a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_5d43276a-1789-49ba-81b6-d645f574ba04" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_84f05f50-eb11-4cec-8c84-ae11a54c253a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_SeniorConvertibleNotes2026Member_caebe403-1cf8-4d1f-bfa7-a2ae0fadc56b" xlink:href="open-20230630.xsd#open_SeniorConvertibleNotes2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_84f05f50-eb11-4cec-8c84-ae11a54c253a" xlink:to="loc_open_SeniorConvertibleNotes2026Member_caebe403-1cf8-4d1f-bfa7-a2ae0fadc56b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_f78afa5e-464d-4d42-9684-deb830a5aae2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ed37e808-c38d-4a0f-9d77-433c052a15be" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_f78afa5e-464d-4d42-9684-deb830a5aae2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f78afa5e-464d-4d42-9684-deb830a5aae2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f78afa5e-464d-4d42-9684-deb830a5aae2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f78afa5e-464d-4d42-9684-deb830a5aae2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_393fe6d7-704c-4939-acf7-86c0159c5c1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f78afa5e-464d-4d42-9684-deb830a5aae2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_393fe6d7-704c-4939-acf7-86c0159c5c1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_5b58b1f4-0e92-46c1-84da-f6a2d22f3dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_393fe6d7-704c-4939-acf7-86c0159c5c1b" xlink:to="loc_us-gaap_ConvertibleDebtMember_5b58b1f4-0e92-46c1-84da-f6a2d22f3dc2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSAmortizedCostDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CASHCASHEQUIVALENTSANDINVESTMENTSAmortizedCostDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSAmortizedCostDetails" xlink:type="extended" id="ie5739e7542d14bb5a644a563ffc7fd73_CASHCASHEQUIVALENTSANDINVESTMENTSAmortizedCostDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_0b4b7e8c-23df-4b0d-a306-dfc0d311d029" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_0b4b7e8c-23df-4b0d-a306-dfc0d311d029" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_17d3e93c-4a7f-4602-8951-ee289351a7b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_17d3e93c-4a7f-4602-8951-ee289351a7b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_2ed7d44b-5d06-4d0c-b3f1-3d268cbec9c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_2ed7d44b-5d06-4d0c-b3f1-3d268cbec9c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_ee4c1ea5-e0b0-491e-89c7-a35fcfe61ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_ee4c1ea5-e0b0-491e-89c7-a35fcfe61ec0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e1526243-ed1b-4fbd-aaaf-f0e86b5815a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e1526243-ed1b-4fbd-aaaf-f0e86b5815a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_DebtSecuritiesAvailableForSaleCashAndCashEquivalents_4cc10297-d3b5-47c4-86a0-5a274f40edfa" xlink:href="open-20230630.xsd#open_DebtSecuritiesAvailableForSaleCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_DebtSecuritiesAvailableForSaleCashAndCashEquivalents_4cc10297-d3b5-47c4-86a0-5a274f40edfa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_DebtSecuritiesAvailableForSaleMarketableSecurities_9b2777a9-a42d-4254-a9ac-882a3980e530" xlink:href="open-20230630.xsd#open_DebtSecuritiesAvailableForSaleMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_DebtSecuritiesAvailableForSaleMarketableSecurities_9b2777a9-a42d-4254-a9ac-882a3980e530" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_4cd58bcc-e2b4-47ae-bee2-c5d22ebd4ea7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_4cd58bcc-e2b4-47ae-bee2-c5d22ebd4ea7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EquitySecuritiesFVNICashAndCashEquivalents_41dd5db4-4627-4a81-a6ec-9ce6bf78839f" xlink:href="open-20230630.xsd#open_EquitySecuritiesFVNICashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_EquitySecuritiesFVNICashAndCashEquivalents_41dd5db4-4627-4a81-a6ec-9ce6bf78839f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EquitySecuritiesFVNIMarketableSecurities_d52f69a4-15a5-4bad-8a47-c848315f1dbf" xlink:href="open-20230630.xsd#open_EquitySecuritiesFVNIMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_EquitySecuritiesFVNIMarketableSecurities_d52f69a4-15a5-4bad-8a47-c848315f1dbf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_CashCashEquivalentsAndMarketableSecuritiesAmortizedCost_8103d96c-7df0-41df-a244-4c2f53b9e95f" xlink:href="open-20230630.xsd#open_CashCashEquivalentsAndMarketableSecuritiesAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_CashCashEquivalentsAndMarketableSecuritiesAmortizedCost_8103d96c-7df0-41df-a244-4c2f53b9e95f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_CashCashEquivalentsAndMarketableSecurities_fc2764b8-75d9-48a9-87b5-bf589d0faab3" xlink:href="open-20230630.xsd#open_CashCashEquivalentsAndMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_CashCashEquivalentsAndMarketableSecurities_fc2764b8-75d9-48a9-87b5-bf589d0faab3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MarketableSecuritiesCashAndCashEquivalents_02535956-c540-4210-9cc9-d35c470b42a7" xlink:href="open-20230630.xsd#open_MarketableSecuritiesCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_open_MarketableSecuritiesCashAndCashEquivalents_02535956-c540-4210-9cc9-d35c470b42a7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecurities_e64c4d44-4718-4884-a3b5-8e070354d97b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_MarketableSecurities_e64c4d44-4718-4884-a3b5-8e070354d97b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_f07551bd-f2b7-4242-b588-0c4327daad3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04d5277e-47ee-493e-89db-7f1528ecf776" xlink:to="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_f07551bd-f2b7-4242-b588-0c4327daad3e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_8460c7f2-744f-479b-8b3f-a0ba4b712267" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_f07551bd-f2b7-4242-b588-0c4327daad3e" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_8460c7f2-744f-479b-8b3f-a0ba4b712267" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8460c7f2-744f-479b-8b3f-a0ba4b712267_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_8460c7f2-744f-479b-8b3f-a0ba4b712267" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8460c7f2-744f-479b-8b3f-a0ba4b712267_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c7962c27-ebaa-4a7d-a091-7a13cfb9ba19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_8460c7f2-744f-479b-8b3f-a0ba4b712267" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c7962c27-ebaa-4a7d-a091-7a13cfb9ba19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_e6bb3546-3ebb-4687-9460-f331f3bc9a88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c7962c27-ebaa-4a7d-a091-7a13cfb9ba19" xlink:to="loc_us-gaap_CashMember_e6bb3546-3ebb-4687-9460-f331f3bc9a88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_e2582e69-964e-410f-88b8-5bb1c307a9ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c7962c27-ebaa-4a7d-a091-7a13cfb9ba19" xlink:to="loc_us-gaap_MoneyMarketFundsMember_e2582e69-964e-410f-88b8-5bb1c307a9ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_7a2dcd55-9150-4571-a1b8-152f1b2b43cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_f07551bd-f2b7-4242-b588-0c4327daad3e" xlink:to="loc_us-gaap_FinancialInstrumentAxis_7a2dcd55-9150-4571-a1b8-152f1b2b43cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7a2dcd55-9150-4571-a1b8-152f1b2b43cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_7a2dcd55-9150-4571-a1b8-152f1b2b43cc" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7a2dcd55-9150-4571-a1b8-152f1b2b43cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fdcaaca0-d1ed-4784-bd24-59b2c10835b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_7a2dcd55-9150-4571-a1b8-152f1b2b43cc" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fdcaaca0-d1ed-4784-bd24-59b2c10835b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_18393fa4-a423-4a68-8536-309bfcac6647" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fdcaaca0-d1ed-4784-bd24-59b2c10835b1" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_18393fa4-a423-4a68-8536-309bfcac6647" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_2200cee5-bb2f-4576-920c-bd9fee50d1ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fdcaaca0-d1ed-4784-bd24-59b2c10835b1" xlink:to="loc_us-gaap_CertificatesOfDepositMember_2200cee5-bb2f-4576-920c-bd9fee50d1ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_ccd4fb2b-2574-495e-ba69-b766198e07d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fdcaaca0-d1ed-4784-bd24-59b2c10835b1" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_ccd4fb2b-2574-495e-ba69-b766198e07d3" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSSummaryofDebtSecuritiesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CASHCASHEQUIVALENTSANDINVESTMENTSSummaryofDebtSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSSummaryofDebtSecuritiesDetails" xlink:type="extended" id="i37d2cf5e0a9f468b85a2a166feac4981_CASHCASHEQUIVALENTSANDINVESTMENTSSummaryofDebtSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_a4f1dc2f-abc2-4556-a050-22b71b48480f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_a4f1dc2f-abc2-4556-a050-22b71b48480f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_07f36f13-a060-4f1a-96c3-9ad0692378d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_07f36f13-a060-4f1a-96c3-9ad0692378d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_e72d6c66-3cde-42fc-abcc-29f4d479068d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_e72d6c66-3cde-42fc-abcc-29f4d479068d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_a43acdfc-1aee-40fe-8419-64770e38c31e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_a43acdfc-1aee-40fe-8419-64770e38c31e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_1f91589d-bafa-4dbb-8414-4fe0c543fb7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_1f91589d-bafa-4dbb-8414-4fe0c543fb7c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_68dd0878-b1e0-4a8c-a97e-4dcd2f49560a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_68dd0878-b1e0-4a8c-a97e-4dcd2f49560a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_b804b2e4-9f95-40a1-8054-8b293bf22dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_04cfbcef-df41-4c1f-a132-675bfdbd20ed" xlink:to="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_b804b2e4-9f95-40a1-8054-8b293bf22dc7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_06af22b5-a792-499c-9ec6-893566bb778b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_b804b2e4-9f95-40a1-8054-8b293bf22dc7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_06af22b5-a792-499c-9ec6-893566bb778b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_06af22b5-a792-499c-9ec6-893566bb778b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_06af22b5-a792-499c-9ec6-893566bb778b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_06af22b5-a792-499c-9ec6-893566bb778b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e23373a1-dd6c-4640-90ec-cee0321bb14a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_06af22b5-a792-499c-9ec6-893566bb778b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e23373a1-dd6c-4640-90ec-cee0321bb14a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_1252fcf5-2462-4655-ab13-1c286286d05b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e23373a1-dd6c-4640-90ec-cee0321bb14a" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_1252fcf5-2462-4655-ab13-1c286286d05b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_160a68ad-af0b-444f-9c3a-e319842fb92e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e23373a1-dd6c-4640-90ec-cee0321bb14a" xlink:to="loc_us-gaap_CertificatesOfDepositMember_160a68ad-af0b-444f-9c3a-e319842fb92e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_51f1fb89-3127-4a53-87c4-4efe190eba0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e23373a1-dd6c-4640-90ec-cee0321bb14a" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_51f1fb89-3127-4a53-87c4-4efe190eba0c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSScheduleofContractualMarketableSecuritiesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CASHCASHEQUIVALENTSANDINVESTMENTSScheduleofContractualMarketableSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CASHCASHEQUIVALENTSANDINVESTMENTSScheduleofContractualMarketableSecuritiesDetails" xlink:type="extended" id="i8de72cf2698c48ec90ee1e1b6979cc0f_CASHCASHEQUIVALENTSANDINVESTMENTSScheduleofContractualMarketableSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsLineItems_075fae23-1b7a-4e82-a6a5-3b222c17a82b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_84f441b5-2773-4f0d-baf5-ee578709b623" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_075fae23-1b7a-4e82-a6a5-3b222c17a82b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_84f441b5-2773-4f0d-baf5-ee578709b623" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_72fc0921-1b0e-4845-bd35-436a9791cb40" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_075fae23-1b7a-4e82-a6a5-3b222c17a82b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_72fc0921-1b0e-4845-bd35-436a9791cb40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_8f73e626-a5fb-40cc-9ca3-738f474ed3ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_075fae23-1b7a-4e82-a6a5-3b222c17a82b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_8f73e626-a5fb-40cc-9ca3-738f474ed3ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_56ab7536-663b-4cd9-ad80-37734227b0eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_075fae23-1b7a-4e82-a6a5-3b222c17a82b" xlink:to="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_56ab7536-663b-4cd9-ad80-37734227b0eb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_0190fa12-9187-4bdb-a075-f97d8279453f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_56ab7536-663b-4cd9-ad80-37734227b0eb" xlink:to="loc_us-gaap_FinancialInstrumentAxis_0190fa12-9187-4bdb-a075-f97d8279453f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0190fa12-9187-4bdb-a075-f97d8279453f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_0190fa12-9187-4bdb-a075-f97d8279453f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0190fa12-9187-4bdb-a075-f97d8279453f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_366d8d99-816f-4411-89a4-5dfec5d3fcad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_0190fa12-9187-4bdb-a075-f97d8279453f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_366d8d99-816f-4411-89a4-5dfec5d3fcad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_c3a1ef41-266e-4ab2-b6df-9b1c44c8e4aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_366d8d99-816f-4411-89a4-5dfec5d3fcad" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_c3a1ef41-266e-4ab2-b6df-9b1c44c8e4aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_44590934-82d6-44ca-b796-0e81249acdb0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_366d8d99-816f-4411-89a4-5dfec5d3fcad" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_44590934-82d6-44ca-b796-0e81249acdb0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/VARIABLEINTERESTENTITIESDetails" xlink:type="simple" xlink:href="open-20230630.xsd#VARIABLEINTERESTENTITIESDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/VARIABLEINTERESTENTITIESDetails" xlink:type="extended" id="if2be5f99779f493a8c4b0e54cbda2033_VARIABLEINTERESTENTITIESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_c4219597-1f39-4ffd-b826-426a067cfd16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_c4219597-1f39-4ffd-b826-426a067cfd16" xlink:to="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_4faff3f4-a94f-4095-8014-c27cd48ab5c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_4faff3f4-a94f-4095-8014-c27cd48ab5c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_bb59a98a-8f10-45b5-b24c-799f49aa34f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_bb59a98a-8f10-45b5-b24c-799f49aa34f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRealEstate_77bc7f67-e5b0-4fbf-8813-a78d56915e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:to="loc_us-gaap_InventoryRealEstate_77bc7f67-e5b0-4fbf-8813-a78d56915e4f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_4b4315d9-1239-4349-9ad7-301e14560c13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:to="loc_us-gaap_OtherAssets_4b4315d9-1239-4349-9ad7-301e14560c13" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_b56ca9a9-a30a-4007-b0e1-99bb8c44152c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_10ed3d23-d2f0-4b1d-8857-e6524c1880e5" xlink:to="loc_us-gaap_Assets_b56ca9a9-a30a-4007-b0e1-99bb8c44152c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_7fe8dedf-0074-4e57-acb9-5b02bf6309b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_c4219597-1f39-4ffd-b826-426a067cfd16" xlink:to="loc_us-gaap_LiabilitiesAbstract_7fe8dedf-0074-4e57-acb9-5b02bf6309b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_f5afa4cd-a21c-454d-889e-c3d32a3294f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_7fe8dedf-0074-4e57-acb9-5b02bf6309b6" xlink:to="loc_us-gaap_LineOfCredit_f5afa4cd-a21c-454d-889e-c3d32a3294f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_903f5833-404b-44e8-bab0-94efbd6737e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_7fe8dedf-0074-4e57-acb9-5b02bf6309b6" xlink:to="loc_us-gaap_OtherLiabilities_903f5833-404b-44e8-bab0-94efbd6737e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_bce25783-e295-4bb1-ad03-be865aac3e39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_7fe8dedf-0074-4e57-acb9-5b02bf6309b6" xlink:to="loc_us-gaap_Liabilities_bce25783-e295-4bb1-ad03-be865aac3e39" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_9ee25ce5-7d97-4a0d-86df-aac65436d86c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_c4219597-1f39-4ffd-b826-426a067cfd16" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_9ee25ce5-7d97-4a0d-86df-aac65436d86c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_05bf1837-807c-43e3-a70a-79b1d56f2f7c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_9ee25ce5-7d97-4a0d-86df-aac65436d86c" xlink:to="loc_srt_ConsolidatedEntitiesAxis_05bf1837-807c-43e3-a70a-79b1d56f2f7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_05bf1837-807c-43e3-a70a-79b1d56f2f7c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_05bf1837-807c-43e3-a70a-79b1d56f2f7c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_05bf1837-807c-43e3-a70a-79b1d56f2f7c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_956145ec-9294-4f0e-9b60-bd30e83d3739" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_05bf1837-807c-43e3-a70a-79b1d56f2f7c" xlink:to="loc_srt_ConsolidatedEntitiesDomain_956145ec-9294-4f0e-9b60-bd30e83d3739" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_01e6ae97-4a05-48de-b7ec-290c65b177bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_956145ec-9294-4f0e-9b60-bd30e83d3739" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_01e6ae97-4a05-48de-b7ec-290c65b177bf" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTSummaryofCreditFacilitiesandLongTermDebtDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTSummaryofCreditFacilitiesandLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTSummaryofCreditFacilitiesandLongTermDebtDetails" xlink:type="extended" id="ia1a96925955044e5a800703037e4c1c7_CREDITFACILITIESANDLONGTERMDEBTSummaryofCreditFacilitiesandLongTermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_65cf9fad-5e58-4efd-a089-44ca6e580184" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_65cf9fad-5e58-4efd-a089-44ca6e580184" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_LongTermDebtGrossCurrent_b7a49d1f-1377-43c1-923e-11f031a94e35" xlink:href="open-20230630.xsd#open_LongTermDebtGrossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_open_LongTermDebtGrossCurrent_b7a49d1f-1377-43c1-923e-11f031a94e35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_c66b1de6-4180-460b-a2ac-73b44763acb8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_LongTermDebtCurrent_c66b1de6-4180-460b-a2ac-73b44763acb8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_LongTermDebtGrossNoncurrent_68061151-7ef2-44bc-b686-c5eb52b44b38" xlink:href="open-20230630.xsd#open_LongTermDebtGrossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_open_LongTermDebtGrossNoncurrent_68061151-7ef2-44bc-b686-c5eb52b44b38" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsCurrentNet_e481a144-4a5e-4de0-af5a-3965a1365ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsCurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_DeferredFinanceCostsCurrentNet_e481a144-4a5e-4de0-af5a-3965a1365ddc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_4722dec4-77ef-4fcd-88f5-b24bf0985fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_4722dec4-77ef-4fcd-88f5-b24bf0985fb4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_729d688b-c609-437d-969f-bfcbed7f4d7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_729d688b-c609-437d-969f-bfcbed7f4d7f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_448c8faa-52d9-4aa2-bada-1bb4efcfbf85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_448c8faa-52d9-4aa2-bada-1bb4efcfbf85" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_1149c66d-3c79-40c7-a1bb-47d9c03f7480" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b6c8d59b-ee57-429b-8df9-c13769a965c2" xlink:to="loc_us-gaap_DebtInstrumentTable_1149c66d-3c79-40c7-a1bb-47d9c03f7480" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1149c66d-3c79-40c7-a1bb-47d9c03f7480" xlink:to="loc_us-gaap_CreditFacilityAxis_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0" xlink:to="loc_us-gaap_CreditFacilityDomain_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_eb8c8f3f-0a96-41b6-a7b6-ffed1b924ac0" xlink:to="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20182Member_9c6c3ca8-da30-4c7a-88dd-7f9fed14ddf6" xlink:href="open-20230630.xsd#open_RevolvingFacility20182Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20182Member_9c6c3ca8-da30-4c7a-88dd-7f9fed14ddf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20183Member_a976b3bd-525e-487e-95b1-fb3892a73042" xlink:href="open-20230630.xsd#open_RevolvingFacility20183Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20183Member_a976b3bd-525e-487e-95b1-fb3892a73042" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20191Member_871b57af-543a-4ce8-828f-457e6faa2fbe" xlink:href="open-20230630.xsd#open_RevolvingFacility20191Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20191Member_871b57af-543a-4ce8-828f-457e6faa2fbe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20192Member_c5864337-5c03-488e-a1d8-55300c16008a" xlink:href="open-20230630.xsd#open_RevolvingFacility20192Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20192Member_c5864337-5c03-488e-a1d8-55300c16008a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20193Member_4b3b206c-9c61-4856-aba1-c1efce920f00" xlink:href="open-20230630.xsd#open_RevolvingFacility20193Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20193Member_4b3b206c-9c61-4856-aba1-c1efce920f00" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RevolvingFacility20221Member_1b71c447-b724-47a9-8d93-5d41545289f9" xlink:href="open-20230630.xsd#open_RevolvingFacility20221Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_RevolvingFacility20221Member_1b71c447-b724-47a9-8d93-5d41545289f9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2021S1Member_532a55ff-40f7-4669-820b-ee2c227a02e3" xlink:href="open-20230630.xsd#open_TermDebtFacility2021S1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2021S1Member_532a55ff-40f7-4669-820b-ee2c227a02e3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2021S2Member_3ff0f241-1043-41e9-9751-3f4ede1d5409" xlink:href="open-20230630.xsd#open_TermDebtFacility2021S2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2021S2Member_3ff0f241-1043-41e9-9751-3f4ede1d5409" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2021S3Member_1a0c3237-047c-474a-86ee-6c6f82e34a2c" xlink:href="open-20230630.xsd#open_TermDebtFacility2021S3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2021S3Member_1a0c3237-047c-474a-86ee-6c6f82e34a2c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2022S1Member_423fa374-d7f4-48f0-b4be-d038f524c0f2" xlink:href="open-20230630.xsd#open_TermDebtFacility2022S1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2022S1Member_423fa374-d7f4-48f0-b4be-d038f524c0f2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2022S2Member_5f9dc456-fad1-4010-af7f-e05ebb506041" xlink:href="open-20230630.xsd#open_TermDebtFacility2022S2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2022S2Member_5f9dc456-fad1-4010-af7f-e05ebb506041" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2020M1Member_690041a7-ad18-4abd-8de7-9b92906fcb88" xlink:href="open-20230630.xsd#open_TermDebtFacility2020M1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2020M1Member_690041a7-ad18-4abd-8de7-9b92906fcb88" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TermDebtFacility2022M1Member_bf4d308f-b48a-4415-892b-580d901a90d1" xlink:href="open-20230630.xsd#open_TermDebtFacility2022M1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3afd9bb2-7380-448d-8152-df1a71531a13" xlink:to="loc_open_TermDebtFacility2022M1Member_bf4d308f-b48a-4415-892b-580d901a90d1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_31c5e398-25e7-4a2b-b701-c937d4a8101e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1149c66d-3c79-40c7-a1bb-47d9c03f7480" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_31c5e398-25e7-4a2b-b701-c937d4a8101e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_31c5e398-25e7-4a2b-b701-c937d4a8101e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_31c5e398-25e7-4a2b-b701-c937d4a8101e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_31c5e398-25e7-4a2b-b701-c937d4a8101e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ccaab680-70c6-45a7-b44f-928580272918" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_31c5e398-25e7-4a2b-b701-c937d4a8101e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ccaab680-70c6-45a7-b44f-928580272918" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_3c8dfa4d-245d-4ed7-9470-c05664b6fc8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ccaab680-70c6-45a7-b44f-928580272918" xlink:to="loc_us-gaap_LineOfCreditMember_3c8dfa4d-245d-4ed7-9470-c05664b6fc8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6070baa0-d277-45b3-90b9-4b311c5532a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1149c66d-3c79-40c7-a1bb-47d9c03f7480" xlink:to="loc_us-gaap_DebtInstrumentAxis_6070baa0-d277-45b3-90b9-4b311c5532a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6070baa0-d277-45b3-90b9-4b311c5532a7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6070baa0-d277-45b3-90b9-4b311c5532a7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6070baa0-d277-45b3-90b9-4b311c5532a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a9f44640-d36d-4ff4-ad18-5c408ebd868e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6070baa0-d277-45b3-90b9-4b311c5532a7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a9f44640-d36d-4ff4-ad18-5c408ebd868e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_AssetBackSeniorCreditFacilityMember_3b9ca8d5-9961-41c4-8c06-edda4b2e1b08" xlink:href="open-20230630.xsd#open_AssetBackSeniorCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a9f44640-d36d-4ff4-ad18-5c408ebd868e" xlink:to="loc_open_AssetBackSeniorCreditFacilityMember_3b9ca8d5-9961-41c4-8c06-edda4b2e1b08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MezzanineTermDebtFacilitiesMember_63e22ff2-1ee8-4686-81aa-a2b3b050ccb9" xlink:href="open-20230630.xsd#open_MezzanineTermDebtFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a9f44640-d36d-4ff4-ad18-5c408ebd868e" xlink:to="loc_open_MezzanineTermDebtFacilitiesMember_63e22ff2-1ee8-4686-81aa-a2b3b050ccb9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTNonRecourseAssetbackedDebtDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTNonRecourseAssetbackedDebtDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTNonRecourseAssetbackedDebtDetails" xlink:type="extended" id="i3fda6edd4f96443d86780bfc557a6e6c_CREDITFACILITIESANDLONGTERMDEBTNonRecourseAssetbackedDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_edbc06fc-ae2c-484a-9d7b-186380ee5996" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_f24ebe21-cc57-42da-8690-54d459de7359" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_edbc06fc-ae2c-484a-9d7b-186380ee5996" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_f24ebe21-cc57-42da-8690-54d459de7359" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_LineOfCreditFacilityFullyCommittedMaximumBorrowingCapacity_fa29b312-8244-407a-9112-f35a55e002ef" xlink:href="open-20230630.xsd#open_LineOfCreditFacilityFullyCommittedMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_edbc06fc-ae2c-484a-9d7b-186380ee5996" xlink:to="loc_open_LineOfCreditFacilityFullyCommittedMaximumBorrowingCapacity_fa29b312-8244-407a-9112-f35a55e002ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_LineOfCreditFacilityFullyCommittedBorrowingCapacity_78e500b6-4967-4737-9789-bfba175e91bd" xlink:href="open-20230630.xsd#open_LineOfCreditFacilityFullyCommittedBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_edbc06fc-ae2c-484a-9d7b-186380ee5996" xlink:to="loc_open_LineOfCreditFacilityFullyCommittedBorrowingCapacity_78e500b6-4967-4737-9789-bfba175e91bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_93989a16-8d86-486a-b142-01dd8a241cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_edbc06fc-ae2c-484a-9d7b-186380ee5996" xlink:to="loc_us-gaap_DebtInstrumentTable_93989a16-8d86-486a-b142-01dd8a241cf7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_dc6cb623-19c3-4e49-bbf2-a9851a43d220" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_93989a16-8d86-486a-b142-01dd8a241cf7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_dc6cb623-19c3-4e49-bbf2-a9851a43d220" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_dc6cb623-19c3-4e49-bbf2-a9851a43d220_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_dc6cb623-19c3-4e49-bbf2-a9851a43d220" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_dc6cb623-19c3-4e49-bbf2-a9851a43d220_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d637c7a9-15a7-4a21-b5d8-5d941cb2f53f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_dc6cb623-19c3-4e49-bbf2-a9851a43d220" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d637c7a9-15a7-4a21-b5d8-5d941cb2f53f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_56c6b214-15cb-48cf-a0eb-a912bdd9ff53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d637c7a9-15a7-4a21-b5d8-5d941cb2f53f" xlink:to="loc_us-gaap_LineOfCreditMember_56c6b214-15cb-48cf-a0eb-a912bdd9ff53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_5dac7aff-8bcb-4c3f-87b0-b35798f26e21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d637c7a9-15a7-4a21-b5d8-5d941cb2f53f" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_5dac7aff-8bcb-4c3f-87b0-b35798f26e21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_84b69efb-17df-4ac8-bdb4-43e5961d3e91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_93989a16-8d86-486a-b142-01dd8a241cf7" xlink:to="loc_us-gaap_DebtInstrumentAxis_84b69efb-17df-4ac8-bdb4-43e5961d3e91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_84b69efb-17df-4ac8-bdb4-43e5961d3e91_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_84b69efb-17df-4ac8-bdb4-43e5961d3e91" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_84b69efb-17df-4ac8-bdb4-43e5961d3e91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_62b04ca7-a6ed-482f-9b3b-c7ed8358207a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_84b69efb-17df-4ac8-bdb4-43e5961d3e91" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_62b04ca7-a6ed-482f-9b3b-c7ed8358207a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_AssetBackSeniorCreditFacilityAndMezzanineTermDebtFacilitiesMember_5334d901-f5a8-4c2d-b0e0-1cf8be700cd8" xlink:href="open-20230630.xsd#open_AssetBackSeniorCreditFacilityAndMezzanineTermDebtFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_62b04ca7-a6ed-482f-9b3b-c7ed8358207a" xlink:to="loc_open_AssetBackSeniorCreditFacilityAndMezzanineTermDebtFacilitiesMember_5334d901-f5a8-4c2d-b0e0-1cf8be700cd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_AssetBackSeniorCreditFacilityMember_3c1fc98a-fab1-4394-ba70-69f4cf0555e8" xlink:href="open-20230630.xsd#open_AssetBackSeniorCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_62b04ca7-a6ed-482f-9b3b-c7ed8358207a" xlink:to="loc_open_AssetBackSeniorCreditFacilityMember_3c1fc98a-fab1-4394-ba70-69f4cf0555e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MezzanineTermDebtFacilitiesMember_87bbd34e-cf29-4795-8b65-b306ada1fb0d" xlink:href="open-20230630.xsd#open_MezzanineTermDebtFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_62b04ca7-a6ed-482f-9b3b-c7ed8358207a" xlink:to="loc_open_MezzanineTermDebtFacilitiesMember_87bbd34e-cf29-4795-8b65-b306ada1fb0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_a8f286cf-3899-4fa1-89d4-71ef40d03be4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_93989a16-8d86-486a-b142-01dd8a241cf7" xlink:to="loc_us-gaap_CreditFacilityAxis_a8f286cf-3899-4fa1-89d4-71ef40d03be4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_a8f286cf-3899-4fa1-89d4-71ef40d03be4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_a8f286cf-3899-4fa1-89d4-71ef40d03be4" xlink:to="loc_us-gaap_CreditFacilityDomain_a8f286cf-3899-4fa1-89d4-71ef40d03be4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_bfdfc5be-22ce-4308-8a40-fc848df688b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_a8f286cf-3899-4fa1-89d4-71ef40d03be4" xlink:to="loc_us-gaap_CreditFacilityDomain_bfdfc5be-22ce-4308-8a40-fc848df688b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MultipleSeniorRevolvingCreditFacilitiesMember_5ba6a4fe-bf7b-467c-af41-938a9a235033" xlink:href="open-20230630.xsd#open_MultipleSeniorRevolvingCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bfdfc5be-22ce-4308-8a40-fc848df688b5" xlink:to="loc_open_MultipleSeniorRevolvingCreditFacilitiesMember_5ba6a4fe-bf7b-467c-af41-938a9a235033" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MultipleTermLoanFacilitiesMember_29c7bf9f-03bd-4441-a939-c69692745cca" xlink:href="open-20230630.xsd#open_MultipleTermLoanFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bfdfc5be-22ce-4308-8a40-fc848df688b5" xlink:to="loc_open_MultipleTermLoanFacilitiesMember_29c7bf9f-03bd-4441-a939-c69692745cca" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTAssetBackedSeniorCreditFacilitiesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTAssetBackedSeniorCreditFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTAssetBackedSeniorCreditFacilitiesDetails" xlink:type="extended" id="i80d38250933547068e78a54cceaa067c_CREDITFACILITIESANDLONGTERMDEBTAssetBackedSeniorCreditFacilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_e072691e-6d42-48d7-a0f3-d54e05603fde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_b237c623-5cee-4de8-94ea-d4ab4f1de611" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e072691e-6d42-48d7-a0f3-d54e05603fde" xlink:to="loc_us-gaap_DebtInstrumentTerm_b237c623-5cee-4de8-94ea-d4ab4f1de611" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_DebtInstrumentTermWithdrawalPeriodMaximum_aafc9e54-3db0-440a-93ad-dfed2c43e89e" xlink:href="open-20230630.xsd#open_DebtInstrumentTermWithdrawalPeriodMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e072691e-6d42-48d7-a0f3-d54e05603fde" xlink:to="loc_open_DebtInstrumentTermWithdrawalPeriodMaximum_aafc9e54-3db0-440a-93ad-dfed2c43e89e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_16cb1941-558f-4218-9064-6e69fc0fb3f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e072691e-6d42-48d7-a0f3-d54e05603fde" xlink:to="loc_us-gaap_DebtInstrumentTable_16cb1941-558f-4218-9064-6e69fc0fb3f1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_16cb1941-558f-4218-9064-6e69fc0fb3f1" xlink:to="loc_us-gaap_CreditFacilityAxis_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f" xlink:to="loc_us-gaap_CreditFacilityDomain_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_74c8746c-83d6-48f4-a773-4c3663cbe8fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_7944159e-3d2b-4b9a-b2e0-e79a9ad1006f" xlink:to="loc_us-gaap_CreditFacilityDomain_74c8746c-83d6-48f4-a773-4c3663cbe8fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MultipleSeniorRevolvingCreditFacilitiesMember_2498d483-ad41-491e-9986-61b9fd097311" xlink:href="open-20230630.xsd#open_MultipleSeniorRevolvingCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_74c8746c-83d6-48f4-a773-4c3663cbe8fd" xlink:to="loc_open_MultipleSeniorRevolvingCreditFacilitiesMember_2498d483-ad41-491e-9986-61b9fd097311" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MultipleTermLoanFacilitiesMember_48803c7a-047a-47c0-aac1-8a21985ca8c7" xlink:href="open-20230630.xsd#open_MultipleTermLoanFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_74c8746c-83d6-48f4-a773-4c3663cbe8fd" xlink:to="loc_open_MultipleTermLoanFacilitiesMember_48803c7a-047a-47c0-aac1-8a21985ca8c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_9f844a50-1eca-4fbd-841c-ac36b399d311" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_16cb1941-558f-4218-9064-6e69fc0fb3f1" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_9f844a50-1eca-4fbd-841c-ac36b399d311" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9f844a50-1eca-4fbd-841c-ac36b399d311_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9f844a50-1eca-4fbd-841c-ac36b399d311" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9f844a50-1eca-4fbd-841c-ac36b399d311_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fae662cb-1c12-4200-9dcd-40a53ffe6881" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9f844a50-1eca-4fbd-841c-ac36b399d311" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fae662cb-1c12-4200-9dcd-40a53ffe6881" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_cf43d980-d411-4c1d-bfe8-6dbf2d3499a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fae662cb-1c12-4200-9dcd-40a53ffe6881" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_cf43d980-d411-4c1d-bfe8-6dbf2d3499a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_2f6032dc-f375-4180-bd34-49b7b94225e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_16cb1941-558f-4218-9064-6e69fc0fb3f1" xlink:to="loc_us-gaap_DebtInstrumentAxis_2f6032dc-f375-4180-bd34-49b7b94225e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2f6032dc-f375-4180-bd34-49b7b94225e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_2f6032dc-f375-4180-bd34-49b7b94225e1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2f6032dc-f375-4180-bd34-49b7b94225e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b41e4ad0-4abb-428a-bf7e-bed54d60b18b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_2f6032dc-f375-4180-bd34-49b7b94225e1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b41e4ad0-4abb-428a-bf7e-bed54d60b18b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_AssetBackSeniorCreditFacilityMember_b047b7d6-92af-4d4e-aeef-add8dd8b1ea7" xlink:href="open-20230630.xsd#open_AssetBackSeniorCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b41e4ad0-4abb-428a-bf7e-bed54d60b18b" xlink:to="loc_open_AssetBackSeniorCreditFacilityMember_b047b7d6-92af-4d4e-aeef-add8dd8b1ea7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTAssetbackedMezzanineTermDebtFacilitiesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTAssetbackedMezzanineTermDebtFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTAssetbackedMezzanineTermDebtFacilitiesDetails" xlink:type="extended" id="i01509971d4384687808ad7ab1fe5bbab_CREDITFACILITIESANDLONGTERMDEBTAssetbackedMezzanineTermDebtFacilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_73e6f9d4-0476-4e14-bb0a-cead75c5a267" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_DebtInstrumentTermWithdrawalPeriodMaximum_af5fb178-828f-4df1-be92-f3858357dd79" xlink:href="open-20230630.xsd#open_DebtInstrumentTermWithdrawalPeriodMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_73e6f9d4-0476-4e14-bb0a-cead75c5a267" xlink:to="loc_open_DebtInstrumentTermWithdrawalPeriodMaximum_af5fb178-828f-4df1-be92-f3858357dd79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestrictedAssets_ba31df3d-5a3e-4f76-bb29-4e11a04c68ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherRestrictedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_73e6f9d4-0476-4e14-bb0a-cead75c5a267" xlink:to="loc_us-gaap_OtherRestrictedAssets_ba31df3d-5a3e-4f76-bb29-4e11a04c68ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_e1644daa-caa1-4f2a-a80c-cfdad58870f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_73e6f9d4-0476-4e14-bb0a-cead75c5a267" xlink:to="loc_us-gaap_DebtInstrumentTable_e1644daa-caa1-4f2a-a80c-cfdad58870f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_06e23cfd-4a39-4304-91ba-68e411f21184" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e1644daa-caa1-4f2a-a80c-cfdad58870f2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_06e23cfd-4a39-4304-91ba-68e411f21184" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_06e23cfd-4a39-4304-91ba-68e411f21184_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_06e23cfd-4a39-4304-91ba-68e411f21184" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_06e23cfd-4a39-4304-91ba-68e411f21184_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_8edd48e4-64ce-4273-b3c6-6af2509ddf9a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_06e23cfd-4a39-4304-91ba-68e411f21184" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_8edd48e4-64ce-4273-b3c6-6af2509ddf9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_4acfb3d2-1cec-466b-9bef-fc071e3e4ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_8edd48e4-64ce-4273-b3c6-6af2509ddf9a" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_4acfb3d2-1cec-466b-9bef-fc071e3e4ad7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_d62a7779-ae6b-407c-b3c3-3092691a6d02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e1644daa-caa1-4f2a-a80c-cfdad58870f2" xlink:to="loc_us-gaap_DebtInstrumentAxis_d62a7779-ae6b-407c-b3c3-3092691a6d02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d62a7779-ae6b-407c-b3c3-3092691a6d02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_d62a7779-ae6b-407c-b3c3-3092691a6d02" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d62a7779-ae6b-407c-b3c3-3092691a6d02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b8a76e56-72be-4685-96b9-ca2a423259f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_d62a7779-ae6b-407c-b3c3-3092691a6d02" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b8a76e56-72be-4685-96b9-ca2a423259f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MezzanineTermDebtFacilitiesMember_9cccc4d2-6342-4604-a24c-f60a848c00bb" xlink:href="open-20230630.xsd#open_MezzanineTermDebtFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b8a76e56-72be-4685-96b9-ca2a423259f8" xlink:to="loc_open_MezzanineTermDebtFacilitiesMember_9cccc4d2-6342-4604-a24c-f60a848c00bb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTConvertibleSeniorNotesDetails" xlink:type="extended" id="i190fd313b6e4499993f841730a380434_CREDITFACILITIESANDLONGTERMDEBTConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d68ea24d-feec-49c3-900c-5075da776986" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d68ea24d-feec-49c3-900c-5075da776986" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_83247357-1631-47e4-a4b9-a50484ae4691" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_83247357-1631-47e4-a4b9-a50484ae4691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_ab3fb836-77be-4dec-a21c-5a517e92b188" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_ab3fb836-77be-4dec-a21c-5a517e92b188" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_f95e6752-835d-403c-b0da-5e37b16179bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_f95e6752-835d-403c-b0da-5e37b16179bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_46c3ce7c-86a4-47cf-9ead-fc23cc80497b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_LongTermDebt_46c3ce7c-86a4-47cf-9ead-fc23cc80497b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_921f96ba-1e85-408c-8aff-a57749ba6a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_921f96ba-1e85-408c-8aff-a57749ba6a8b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_f5b3fffc-abe9-4e4c-83be-d7a2e00a2686" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_f5b3fffc-abe9-4e4c-83be-d7a2e00a2686" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_6c1e900b-bfaf-4129-9807-500629e127d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_6c1e900b-bfaf-4129-9807-500629e127d2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_bcf05c75-0583-4fc4-8d90-c8ad6f15b7ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_bcf05c75-0583-4fc4-8d90-c8ad6f15b7ab" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfConvertibleDebt_c3efa384-694a-4501-a92a-00c7244ace12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_RepaymentsOfConvertibleDebt_c3efa384-694a-4501-a92a-00c7244ace12" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_aa93206a-5e6a-47df-bb42-88fdeb4b6c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFeeAmount_b9476c98-8765-4820-a7b7-8b996c322d06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentFeeAmount_b9476c98-8765-4820-a7b7-8b996c322d06" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_9059add8-3fc5-4c2b-b456-fc66a4513139" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_9059add8-3fc5-4c2b-b456-fc66a4513139" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_e94445d1-0332-4eca-b2db-9e761b32daf3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_InterestExpenseDebt_e94445d1-0332-4eca-b2db-9e761b32daf3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c90cf9db-0c33-4e3b-902a-31e43a6de8f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8fa5111e-0a34-4bda-b44a-994d6c05742d" xlink:to="loc_us-gaap_DebtInstrumentTable_c90cf9db-0c33-4e3b-902a-31e43a6de8f5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c90cf9db-0c33-4e3b-902a-31e43a6de8f5" xlink:to="loc_us-gaap_DebtInstrumentAxis_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_da06e98a-0229-4eb7-b808-c8aa34ae4bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_f904fb31-cf1b-41f6-b3ec-4ea9b885cbdb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_da06e98a-0229-4eb7-b808-c8aa34ae4bf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_SeniorConvertibleNotes2026Member_4834a3b9-fbbe-4927-8802-e482d1b0bdf8" xlink:href="open-20230630.xsd#open_SeniorConvertibleNotes2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da06e98a-0229-4eb7-b808-c8aa34ae4bf3" xlink:to="loc_open_SeniorConvertibleNotes2026Member_4834a3b9-fbbe-4927-8802-e482d1b0bdf8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_Repurchased2026NotesMember_b9309fc3-7b2c-40c5-9d2b-14a5d6b73ef6" xlink:href="open-20230630.xsd#open_Repurchased2026NotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da06e98a-0229-4eb7-b808-c8aa34ae4bf3" xlink:to="loc_open_Repurchased2026NotesMember_b9309fc3-7b2c-40c5-9d2b-14a5d6b73ef6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_AdditionalRepurchased2026NotesMember_d5e1bf0f-644d-482d-b28f-c05a2f1a378d" xlink:href="open-20230630.xsd#open_AdditionalRepurchased2026NotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da06e98a-0229-4eb7-b808-c8aa34ae4bf3" xlink:to="loc_open_AdditionalRepurchased2026NotesMember_d5e1bf0f-644d-482d-b28f-c05a2f1a378d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_12af7162-3371-4b99-b957-96d56964863f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c90cf9db-0c33-4e3b-902a-31e43a6de8f5" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_12af7162-3371-4b99-b957-96d56964863f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_12af7162-3371-4b99-b957-96d56964863f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_12af7162-3371-4b99-b957-96d56964863f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_12af7162-3371-4b99-b957-96d56964863f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6e83a052-6157-4ab0-949b-b90b52c8987a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_12af7162-3371-4b99-b957-96d56964863f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6e83a052-6157-4ab0-949b-b90b52c8987a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_95cf4746-75a5-42fb-9486-0070b7549e4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6e83a052-6157-4ab0-949b-b90b52c8987a" xlink:to="loc_us-gaap_ConvertibleDebtMember_95cf4746-75a5-42fb-9486-0070b7549e4b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTCappedCallsDetails" xlink:type="simple" xlink:href="open-20230630.xsd#CREDITFACILITIESANDLONGTERMDEBTCappedCallsDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/CREDITFACILITIESANDLONGTERMDEBTCappedCallsDetails" xlink:type="extended" id="i7aa0ed9bc2104dbeb8dac980cf1f2a66_CREDITFACILITIESANDLONGTERMDEBTCappedCallsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_OptionIndexedToIssuersEquityCost_0ee4530b-46ca-4592-bb6b-7ba4804eaf92" xlink:href="open-20230630.xsd#open_OptionIndexedToIssuersEquityCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:to="loc_open_OptionIndexedToIssuersEquityCost_0ee4530b-46ca-4592-bb6b-7ba4804eaf92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_a4fe58e8-4f7a-41cc-ac1a-0d33540891fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_a4fe58e8-4f7a-41cc-ac1a-0d33540891fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_OptionIndexedToIssuersEquityCapPrice_ce4a93ec-b99f-4230-a3a0-9b2d16dd814e" xlink:href="open-20230630.xsd#open_OptionIndexedToIssuersEquityCapPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:to="loc_open_OptionIndexedToIssuersEquityCapPrice_ce4a93ec-b99f-4230-a3a0-9b2d16dd814e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_OptionIndexedToIssuersEquityCapPricePremium_53c22106-bd09-4988-8979-8623f89d1f5f" xlink:href="open-20230630.xsd#open_OptionIndexedToIssuersEquityCapPricePremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:to="loc_open_OptionIndexedToIssuersEquityCapPricePremium_53c22106-bd09-4988-8979-8623f89d1f5f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_7a4afed1-d793-444e-867d-c8b798847eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c04e3ccc-00f3-42ca-bc07-589f597f9db7" xlink:to="loc_us-gaap_DebtInstrumentTable_7a4afed1-d793-444e-867d-c8b798847eaf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityEquityAxis_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityEquityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7a4afed1-d793-444e-867d-c8b798847eaf" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityEquityAxis_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityEquityAxis_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_95528e18-7163-4b24-b7cd-734aa64730c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityEquityAxis_4cbb8ab7-86e4-46a2-9a9f-fd55d377067a" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_95528e18-7163-4b24-b7cd-734aa64730c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CallOptionMember_d9d17de4-75d4-46f8-928b-d8df882de303" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CallOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_95528e18-7163-4b24-b7cd-734aa64730c5" xlink:to="loc_us-gaap_CallOptionMember_d9d17de4-75d4-46f8-928b-d8df882de303" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/FAIRVALUEDISCLOSURESFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="simple" xlink:href="open-20230630.xsd#FAIRVALUEDISCLOSURESFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/FAIRVALUEDISCLOSURESFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="extended" id="i77242d72f3eb42808b7912e62f39c8b5_FAIRVALUEDISCLOSURESFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ce48bd43-198b-4312-92e5-aebe7ec006ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_01cadb3c-9afa-4586-9a2f-296fb32cb89d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ce48bd43-198b-4312-92e5-aebe7ec006ca" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_01cadb3c-9afa-4586-9a2f-296fb32cb89d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesAbstract_2c33c005-e426-4744-bc4f-1570728e30b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketableSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_01cadb3c-9afa-4586-9a2f-296fb32cb89d" xlink:to="loc_us-gaap_MarketableSecuritiesAbstract_2c33c005-e426-4744-bc4f-1570728e30b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_9844c274-60d6-4633-b72f-501fb1f88601" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_2c33c005-e426-4744-bc4f-1570728e30b2" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_9844c274-60d6-4633-b72f-501fb1f88601" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsAbstract_e17ac323-2832-4554-93cf-594cc7316339" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_01cadb3c-9afa-4586-9a2f-296fb32cb89d" xlink:to="loc_us-gaap_OtherAssetsAbstract_e17ac323-2832-4554-93cf-594cc7316339" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_a8dbe5aa-26a8-4ec8-94ed-19200d1e999f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgagesHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_e17ac323-2832-4554-93cf-594cc7316339" xlink:to="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_a8dbe5aa-26a8-4ec8-94ed-19200d1e999f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_ffebcdba-0fe1-4772-bd5e-715f7ba0ee9c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_01cadb3c-9afa-4586-9a2f-296fb32cb89d" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_ffebcdba-0fe1-4772-bd5e-715f7ba0ee9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_cd4b1c17-d35b-4847-8b51-a2c798000de7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ce48bd43-198b-4312-92e5-aebe7ec006ca" xlink:to="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_cd4b1c17-d35b-4847-8b51-a2c798000de7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_17b1225e-44d9-498f-9ca1-cc03b647f3b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_cd4b1c17-d35b-4847-8b51-a2c798000de7" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_17b1225e-44d9-498f-9ca1-cc03b647f3b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_17b1225e-44d9-498f-9ca1-cc03b647f3b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_17b1225e-44d9-498f-9ca1-cc03b647f3b1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_17b1225e-44d9-498f-9ca1-cc03b647f3b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_ee1b6274-df13-4b2c-8783-6d5c86ac81fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_17b1225e-44d9-498f-9ca1-cc03b647f3b1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_ee1b6274-df13-4b2c-8783-6d5c86ac81fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_87e4ed19-4b5b-4518-8387-5360ef84b8e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_ee1b6274-df13-4b2c-8783-6d5c86ac81fb" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_87e4ed19-4b5b-4518-8387-5360ef84b8e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_a5449be4-c49e-4688-9d8a-f6ef412287c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_cd4b1c17-d35b-4847-8b51-a2c798000de7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_a5449be4-c49e-4688-9d8a-f6ef412287c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a5449be4-c49e-4688-9d8a-f6ef412287c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a5449be4-c49e-4688-9d8a-f6ef412287c1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a5449be4-c49e-4688-9d8a-f6ef412287c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a5449be4-c49e-4688-9d8a-f6ef412287c1" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_13ebe098-04ee-48da-9a66-b50b583d1375" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_13ebe098-04ee-48da-9a66-b50b583d1375" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_1535995e-8c15-41c7-b36a-e790f98f8746" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:to="loc_us-gaap_EquitySecuritiesMember_1535995e-8c15-41c7-b36a-e790f98f8746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_0eb17caf-122e-40c1-98b2-bba663824e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:to="loc_us-gaap_CertificatesOfDepositMember_0eb17caf-122e-40c1-98b2-bba663824e5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_73dab846-16f7-443d-81d4-1fdc2d40ff99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_88a6ac12-3357-441d-94e8-e367cc415707" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_73dab846-16f7-443d-81d4-1fdc2d40ff99" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b12b63df-8db9-4fc4-99cc-9c740f0b919b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_cd4b1c17-d35b-4847-8b51-a2c798000de7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b12b63df-8db9-4fc4-99cc-9c740f0b919b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b12b63df-8db9-4fc4-99cc-9c740f0b919b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b12b63df-8db9-4fc4-99cc-9c740f0b919b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b12b63df-8db9-4fc4-99cc-9c740f0b919b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_750845a1-5fc6-4159-8501-f6885373c17f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b12b63df-8db9-4fc4-99cc-9c740f0b919b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_750845a1-5fc6-4159-8501-f6885373c17f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_0e501f69-5294-4680-99b3-64c55eff6dd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_750845a1-5fc6-4159-8501-f6885373c17f" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_0e501f69-5294-4680-99b3-64c55eff6dd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_90107446-3012-4001-bdf1-66c525e5fa6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_750845a1-5fc6-4159-8501-f6885373c17f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_90107446-3012-4001-bdf1-66c525e5fa6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_b627727c-8a24-48bb-b4e2-a54b96d525ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_750845a1-5fc6-4159-8501-f6885373c17f" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_b627727c-8a24-48bb-b4e2-a54b96d525ef" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/FAIRVALUEDISCLOSURESFairValueDisclosureofAssetsandLiabilitiesNotMeasuredatFairValueDetails" xlink:type="simple" xlink:href="open-20230630.xsd#FAIRVALUEDISCLOSURESFairValueDisclosureofAssetsandLiabilitiesNotMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/FAIRVALUEDISCLOSURESFairValueDisclosureofAssetsandLiabilitiesNotMeasuredatFairValueDetails" xlink:type="extended" id="ic715d4ccee91447ab5c570e53fac413e_FAIRVALUEDISCLOSURESFairValueDisclosureofAssetsandLiabilitiesNotMeasuredatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ec4963f1-553a-4a89-97ec-c9730ef1cfe5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_d4ece95e-2e35-4d8f-9086-de6170463bee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ec4963f1-553a-4a89-97ec-c9730ef1cfe5" xlink:to="loc_us-gaap_AssetsAbstract_d4ece95e-2e35-4d8f-9086-de6170463bee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_6e54e5bc-5153-4a39-9fa7-95cea83fd044" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d4ece95e-2e35-4d8f-9086-de6170463bee" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_6e54e5bc-5153-4a39-9fa7-95cea83fd044" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_f2f18768-d8d1-45f0-9a7d-3e9430b0287a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ec4963f1-553a-4a89-97ec-c9730ef1cfe5" xlink:to="loc_us-gaap_LiabilitiesAbstract_f2f18768-d8d1-45f0-9a7d-3e9430b0287a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditFairValueDisclosure_19bd5b86-3179-403a-b4b0-3f3235a37261" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LinesOfCreditFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_f2f18768-d8d1-45f0-9a7d-3e9430b0287a" xlink:to="loc_us-gaap_LinesOfCreditFairValueDisclosure_19bd5b86-3179-403a-b4b0-3f3235a37261" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtFairValueDisclosures_10d96502-800b-45f1-90cc-b00627d479e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleDebtFairValueDisclosures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_f2f18768-d8d1-45f0-9a7d-3e9430b0287a" xlink:to="loc_us-gaap_ConvertibleDebtFairValueDisclosures_10d96502-800b-45f1-90cc-b00627d479e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_79125804-5901-43a3-96f4-15a4bf806ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_ec4963f1-553a-4a89-97ec-c9730ef1cfe5" xlink:to="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_79125804-5901-43a3-96f4-15a4bf806ac2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_b9535b77-66c1-4791-8c37-9c30bfd12d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_79125804-5901-43a3-96f4-15a4bf806ac2" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_b9535b77-66c1-4791-8c37-9c30bfd12d4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_b9535b77-66c1-4791-8c37-9c30bfd12d4f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_b9535b77-66c1-4791-8c37-9c30bfd12d4f" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_b9535b77-66c1-4791-8c37-9c30bfd12d4f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6852953c-c865-4c32-858f-10ba21fe5736" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_b9535b77-66c1-4791-8c37-9c30bfd12d4f" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6852953c-c865-4c32-858f-10ba21fe5736" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_2813fec8-02dc-44db-be84-816bc3e59b87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6852953c-c865-4c32-858f-10ba21fe5736" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_2813fec8-02dc-44db-be84-816bc3e59b87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_d01485f4-d51c-4a85-a898-baf40bc71ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_2813fec8-02dc-44db-be84-816bc3e59b87" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_d01485f4-d51c-4a85-a898-baf40bc71ac2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_7cadb305-7812-417a-9da9-062b00dd2d58" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_2813fec8-02dc-44db-be84-816bc3e59b87" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_7cadb305-7812-417a-9da9-062b00dd2d58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5a1ae597-6367-4c94-b0f9-3e99942e55cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_79125804-5901-43a3-96f4-15a4bf806ac2" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5a1ae597-6367-4c94-b0f9-3e99942e55cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5a1ae597-6367-4c94-b0f9-3e99942e55cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5a1ae597-6367-4c94-b0f9-3e99942e55cc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5a1ae597-6367-4c94-b0f9-3e99942e55cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_dffb2ecd-cd11-438a-b91d-90eae86ae24f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5a1ae597-6367-4c94-b0f9-3e99942e55cc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_dffb2ecd-cd11-438a-b91d-90eae86ae24f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_066555aa-4513-4add-8dc9-371e50394960" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_dffb2ecd-cd11-438a-b91d-90eae86ae24f" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_066555aa-4513-4add-8dc9-371e50394960" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_266c46a7-5892-4ca1-843d-ef7a1d7f2ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_dffb2ecd-cd11-438a-b91d-90eae86ae24f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_266c46a7-5892-4ca1-843d-ef7a1d7f2ef1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_6b270383-3ab0-46c3-87ef-ae798eab4131" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_79125804-5901-43a3-96f4-15a4bf806ac2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_6b270383-3ab0-46c3-87ef-ae798eab4131" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6b270383-3ab0-46c3-87ef-ae798eab4131_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6b270383-3ab0-46c3-87ef-ae798eab4131" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6b270383-3ab0-46c3-87ef-ae798eab4131_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5c6b07be-0291-45d4-b6b6-717d9d490b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6b270383-3ab0-46c3-87ef-ae798eab4131" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5c6b07be-0291-45d4-b6b6-717d9d490b9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_RestrictedCashMember_1df65ffc-9cf7-4592-832d-11de857baaf9" xlink:href="open-20230630.xsd#open_RestrictedCashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5c6b07be-0291-45d4-b6b6-717d9d490b9d" xlink:to="loc_open_RestrictedCashMember_1df65ffc-9cf7-4592-832d-11de857baaf9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/PROPERTYANDEQUIPMENTDetails" xlink:type="simple" xlink:href="open-20230630.xsd#PROPERTYANDEQUIPMENTDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/PROPERTYANDEQUIPMENTDetails" xlink:type="extended" id="idb31791060074c5cb14da922e4e6693d_PROPERTYANDEQUIPMENTDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_6b06c17e-18c8-4282-87b6-75356a63d5e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_6b06c17e-18c8-4282-87b6-75356a63d5e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_b17c09b3-fa74-4ee6-83dd-73fdda03fb83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_b17c09b3-fa74-4ee6-83dd-73fdda03fb83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_78084896-ad75-46f0-9ff6-cbf86ebe28f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_78084896-ad75-46f0-9ff6-cbf86ebe28f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_d5e65526-75ec-4d3f-a5f8-505a86ca8709" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_d5e65526-75ec-4d3f-a5f8-505a86ca8709" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b384c7f-cdab-4c65-9e59-9dd8116d7ec6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_95c65151-4535-4f63-bc22-0b4bfc2eb52c" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b384c7f-cdab-4c65-9e59-9dd8116d7ec6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5694eb33-b0a7-4133-833b-837c0acaf718" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b384c7f-cdab-4c65-9e59-9dd8116d7ec6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5694eb33-b0a7-4133-833b-837c0acaf718" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_5694eb33-b0a7-4133-833b-837c0acaf718_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5694eb33-b0a7-4133-833b-837c0acaf718" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_5694eb33-b0a7-4133-833b-837c0acaf718_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5694eb33-b0a7-4133-833b-837c0acaf718" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareDevelopmentMember_345df82e-6b56-4a22-9876-d17cd67530a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SoftwareDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_us-gaap_SoftwareDevelopmentMember_345df82e-6b56-4a22-9876-d17cd67530a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_SecuritySystemsMember_b343cd1a-15dc-40ae-b05a-52d6f974378e" xlink:href="open-20230630.xsd#open_SecuritySystemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_open_SecuritySystemsMember_b343cd1a-15dc-40ae-b05a-52d6f974378e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_5ba6bc1a-b4bc-4a0e-bbf1-989d72a275e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_us-gaap_ComputerEquipmentMember_5ba6bc1a-b4bc-4a0e-bbf1-989d72a275e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_SoftwareImplementationCostsMember_fdf6636a-4736-403a-8c87-eb0885bbdd7b" xlink:href="open-20230630.xsd#open_SoftwareImplementationCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_open_SoftwareImplementationCostsMember_fdf6636a-4736-403a-8c87-eb0885bbdd7b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_6d514fb3-af1e-4412-9a7e-2e53f617a8e5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_6d514fb3-af1e-4412-9a7e-2e53f617a8e5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OfficeEquipmentMember_e299a4a9-cdd9-4a0b-81e6-f39d08ffbaea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OfficeEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_us-gaap_OfficeEquipmentMember_e299a4a9-cdd9-4a0b-81e6-f39d08ffbaea" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_d28de3d1-a121-49b1-be5a-7dd10ed985f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a99f55e2-4235-4b27-8882-7327dc16b546" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_d28de3d1-a121-49b1-be5a-7dd10ed985f4" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/GOODWILLANDINTANGIBLEASSETSIntangibleAssetsSubjecttoAmortizationDetails" xlink:type="simple" xlink:href="open-20230630.xsd#GOODWILLANDINTANGIBLEASSETSIntangibleAssetsSubjecttoAmortizationDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/GOODWILLANDINTANGIBLEASSETSIntangibleAssetsSubjecttoAmortizationDetails" xlink:type="extended" id="i77779f10fd9e4277a6fb876200b1245a_GOODWILLANDINTANGIBLEASSETSIntangibleAssetsSubjecttoAmortizationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_13bc30b7-97ee-43b0-af6c-3bb0dca154af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_13bc30b7-97ee-43b0-af6c-3bb0dca154af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_39afe5be-7a05-48bd-9943-275319985712" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_39afe5be-7a05-48bd-9943-275319985712" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c14dedc1-14d2-4c79-856a-101f418a5d15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c14dedc1-14d2-4c79-856a-101f418a5d15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_38ec5eb0-4665-4e98-9961-e2c3554b6244" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_38ec5eb0-4665-4e98-9961-e2c3554b6244" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_b8774bbf-ca20-4f19-b3dc-16af5f783f25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_26597542-89ec-4352-9c7d-c8dbf8b63f35" xlink:to="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_b8774bbf-ca20-4f19-b3dc-16af5f783f25" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_b8774bbf-ca20-4f19-b3dc-16af5f783f25" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5204eb27-a190-4240-b894-140cd3441716" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_24c6be4e-c8f8-44f6-816d-65a7ffa4ea7b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5204eb27-a190-4240-b894-140cd3441716" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_1e366851-f890-472d-89b1-a3948ab3268c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5204eb27-a190-4240-b894-140cd3441716" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_1e366851-f890-472d-89b1-a3948ab3268c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_efbe6dde-e485-4879-9206-88685ae2812b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5204eb27-a190-4240-b894-140cd3441716" xlink:to="loc_us-gaap_CustomerRelationshipsMember_efbe6dde-e485-4879-9206-88685ae2812b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_c2a3fb6e-f18c-4152-8e1c-d104fc5bde82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5204eb27-a190-4240-b894-140cd3441716" xlink:to="loc_us-gaap_TrademarksMember_c2a3fb6e-f18c-4152-8e1c-d104fc5bde82" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/SHAREBASEDAWARDSRSUActivityDetails" xlink:type="simple" xlink:href="open-20230630.xsd#SHAREBASEDAWARDSRSUActivityDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/SHAREBASEDAWARDSRSUActivityDetails" xlink:type="extended" id="i408dafb17a5849ee8d2bf52aaae6adb3_SHAREBASEDAWARDSRSUActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ec3a014e-15b5-4103-b2b7-6334534e9256" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ec3a014e-15b5-4103-b2b7-6334534e9256" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_57846a16-fcb3-4d7f-8c22-7c02b494cb7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_57846a16-fcb3-4d7f-8c22-7c02b494cb7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_770541a4-b755-4418-8da8-c4ed3ce37ac5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_770541a4-b755-4418-8da8-c4ed3ce37ac5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_074f3639-4520-4056-b34a-47b8c05d68c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_074f3639-4520-4056-b34a-47b8c05d68c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_645925fa-dce0-4ee8-b17f-c1d4c1934c1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_c24e4cd5-9bb2-4221-bd08-4a8cc8486fad" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_645925fa-dce0-4ee8-b17f-c1d4c1934c1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_5d38fc5f-39ef-4c50-91a9-d1cf2247592c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ec3a014e-15b5-4103-b2b7-6334534e9256" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_c9ac525a-5fd6-4a24-952b-ea1b22342413" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_c9ac525a-5fd6-4a24-952b-ea1b22342413" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d96528d1-1e9a-477b-8d0f-064519a059e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d96528d1-1e9a-477b-8d0f-064519a059e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_4340b7e4-94fb-4c2c-a597-842597ce733d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_4340b7e4-94fb-4c2c-a597-842597ce733d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_0aa7cc86-7e37-44d2-9886-bdee6b974cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_7d6a7bfe-8198-40b4-8e1a-c573dd3d8c03" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_0aa7cc86-7e37-44d2-9886-bdee6b974cc8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_3748780f-e91b-4001-acf5-0fd813e6a1fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2126786d-a3a7-42e6-81b5-d952b3a2e8eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ec3a014e-15b5-4103-b2b7-6334534e9256" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2126786d-a3a7-42e6-81b5-d952b3a2e8eb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_758b2210-544e-4208-b71d-99f5aeb6d16d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_2126786d-a3a7-42e6-81b5-d952b3a2e8eb" xlink:to="loc_us-gaap_AwardTypeAxis_758b2210-544e-4208-b71d-99f5aeb6d16d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_758b2210-544e-4208-b71d-99f5aeb6d16d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_758b2210-544e-4208-b71d-99f5aeb6d16d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_758b2210-544e-4208-b71d-99f5aeb6d16d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6e7523e2-eeb0-4e93-9134-a8c02409764b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_758b2210-544e-4208-b71d-99f5aeb6d16d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6e7523e2-eeb0-4e93-9134-a8c02409764b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_a852fa7e-261c-4844-bd4c-a06aeba79117" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6e7523e2-eeb0-4e93-9134-a8c02409764b" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_a852fa7e-261c-4844-bd4c-a06aeba79117" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_e94cb17b-0ddd-431a-acd0-c11179d8a56d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6e7523e2-eeb0-4e93-9134-a8c02409764b" xlink:to="loc_us-gaap_RestrictedStockMember_e94cb17b-0ddd-431a-acd0-c11179d8a56d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/SHAREBASEDAWARDSESPPDetails" xlink:type="simple" xlink:href="open-20230630.xsd#SHAREBASEDAWARDSESPPDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/SHAREBASEDAWARDSESPPDetails" xlink:type="extended" id="i3f60a475cca8458fa7b966a4f6c25d4e_SHAREBASEDAWARDSESPPDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate_347588b5-dc86-41f2-96b9-e86e7054149e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate_347588b5-dc86-41f2-96b9-e86e7054149e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAnnualContributions_3417fdd0-a7f3-4a25-8507-1a453c7c92d0" xlink:href="open-20230630.xsd#open_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAnnualContributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAnnualContributions_3417fdd0-a7f3-4a25-8507-1a453c7c92d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_NumberOfSharesAllowedPerEmployeePerOfferingPeriod_284c3515-9b83-4e3a-8f50-a65173a41119" xlink:href="open-20230630.xsd#open_NumberOfSharesAllowedPerEmployeePerOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_NumberOfSharesAllowedPerEmployeePerOfferingPeriod_284c3515-9b83-4e3a-8f50-a65173a41119" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EmployeeStockPurchasePlanOfferingPeriodDuration_637723de-21f2-470d-b25b-569edd6f022b" xlink:href="open-20230630.xsd#open_EmployeeStockPurchasePlanOfferingPeriodDuration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_EmployeeStockPurchasePlanOfferingPeriodDuration_637723de-21f2-470d-b25b-569edd6f022b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EmployeeStockPurchasePlanNumberOfPurchasePeriodsDuringOfferingPeriod_6e225bfc-de17-4141-b50e-28dcdb509a09" xlink:href="open-20230630.xsd#open_EmployeeStockPurchasePlanNumberOfPurchasePeriodsDuringOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_EmployeeStockPurchasePlanNumberOfPurchasePeriodsDuringOfferingPeriod_6e225bfc-de17-4141-b50e-28dcdb509a09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EmployeeStockPurchasePlanDurationOfPurchasePeriodsWithinOfferingPeriod_422b2fb1-6a2c-421e-b6ff-10b58738fd54" xlink:href="open-20230630.xsd#open_EmployeeStockPurchasePlanDurationOfPurchasePeriodsWithinOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_EmployeeStockPurchasePlanDurationOfPurchasePeriodsWithinOfferingPeriod_422b2fb1-6a2c-421e-b6ff-10b58738fd54" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_NumberOfSharesAllowedPerPurchasePeriodPerOfferingPeriod_8af8cb0d-2c02-489e-a695-9b5845e9b06d" xlink:href="open-20230630.xsd#open_NumberOfSharesAllowedPerPurchasePeriodPerOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_NumberOfSharesAllowedPerPurchasePeriodPerOfferingPeriod_8af8cb0d-2c02-489e-a695-9b5845e9b06d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_6dcd467e-77b9-4403-a1e4-d4b13d1d5f53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_6dcd467e-77b9-4403-a1e4-d4b13d1d5f53" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEmployeePayrollContributionsWithHeld_3b750b67-807b-4256-89ba-324512247934" xlink:href="open-20230630.xsd#open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEmployeePayrollContributionsWithHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEmployeePayrollContributionsWithHeld_3b750b67-807b-4256-89ba-324512247934" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEstimatedUnrecognizedCompensationExpense_24a48c5a-68bc-4e23-ba3f-86ebd61e98ff" xlink:href="open-20230630.xsd#open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEstimatedUnrecognizedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardEstimatedUnrecognizedCompensationExpense_24a48c5a-68bc-4e23-ba3f-86ebd61e98ff" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardRecognizedOverRemainingTermOfOfferingPeriod_9104c142-9fd7-4915-a937-3372f3295b70" xlink:href="open-20230630.xsd#open_ShareBasedCompensationArrangementByShareBasedPaymentAwardRecognizedOverRemainingTermOfOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_open_ShareBasedCompensationArrangementByShareBasedPaymentAwardRecognizedOverRemainingTermOfOfferingPeriod_9104c142-9fd7-4915-a937-3372f3295b70" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f7f8041c-8539-44a8-932a-ac83b77f8f00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_94d5f8df-8506-4387-aa36-e269d3fb128b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f7f8041c-8539-44a8-932a-ac83b77f8f00" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_65a34237-832e-4b58-a4f7-72c65aba7d45" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f7f8041c-8539-44a8-932a-ac83b77f8f00" xlink:to="loc_us-gaap_AwardTypeAxis_65a34237-832e-4b58-a4f7-72c65aba7d45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65a34237-832e-4b58-a4f7-72c65aba7d45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_65a34237-832e-4b58-a4f7-72c65aba7d45" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_65a34237-832e-4b58-a4f7-72c65aba7d45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f1776202-dad0-4064-ac1e-2766bdbba309" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_65a34237-832e-4b58-a4f7-72c65aba7d45" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f1776202-dad0-4064-ac1e-2766bdbba309" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_276add8d-b64f-47f5-9850-9a1571e1d81d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f1776202-dad0-4064-ac1e-2766bdbba309" xlink:to="loc_us-gaap_EmployeeStockMember_276add8d-b64f-47f5-9850-9a1571e1d81d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_f0339179-9572-47ce-a5ad-2adb99573e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f7f8041c-8539-44a8-932a-ac83b77f8f00" xlink:to="loc_us-gaap_PlanNameAxis_f0339179-9572-47ce-a5ad-2adb99573e3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_f0339179-9572-47ce-a5ad-2adb99573e3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_f0339179-9572-47ce-a5ad-2adb99573e3e" xlink:to="loc_us-gaap_PlanNameDomain_f0339179-9572-47ce-a5ad-2adb99573e3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b4962458-0f87-44f4-a3e0-0d2105dd112e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_f0339179-9572-47ce-a5ad-2adb99573e3e" xlink:to="loc_us-gaap_PlanNameDomain_b4962458-0f87-44f4-a3e0-0d2105dd112e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EmployeeStockPurchasePlanMember_ce0780b9-ae20-42bd-8f44-7dbd175a544f" xlink:href="open-20230630.xsd#open_EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_b4962458-0f87-44f4-a3e0-0d2105dd112e" xlink:to="loc_open_EmployeeStockPurchasePlanMember_ce0780b9-ae20-42bd-8f44-7dbd175a544f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/SHAREBASEDAWARDSFairValueAssumptionsDetails" xlink:type="simple" xlink:href="open-20230630.xsd#SHAREBASEDAWARDSFairValueAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/SHAREBASEDAWARDSFairValueAssumptionsDetails" xlink:type="extended" id="i9e0ffb1de5f64b6bb49d60f5937f6679_SHAREBASEDAWARDSFairValueAssumptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_6bd7651f-5b36-4820-8091-98ccd901c067" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_6bd7651f-5b36-4820-8091-98ccd901c067" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_b9220eaf-7736-416a-89e2-2c44d6a10690" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_b9220eaf-7736-416a-89e2-2c44d6a10690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_343a8385-0d26-4b9c-a82f-503d079e8999" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_343a8385-0d26-4b9c-a82f-503d079e8999" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_39226339-a2ec-490a-97fa-b580cd0ae7a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_39226339-a2ec-490a-97fa-b580cd0ae7a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_f597cb1e-6401-4725-b759-2124283d4639" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_f597cb1e-6401-4725-b759-2124283d4639" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2f5c571b-2cfd-4593-b80b-722146d08bbb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2f5c571b-2cfd-4593-b80b-722146d08bbb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0df33834-898e-4581-8718-831aa8c255ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67648358-6154-4678-a8c8-c214f66fa6b5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0df33834-898e-4581-8718-831aa8c255ba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_280b7081-d318-4c44-b127-3126bf1b8691" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0df33834-898e-4581-8718-831aa8c255ba" xlink:to="loc_us-gaap_AwardTypeAxis_280b7081-d318-4c44-b127-3126bf1b8691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_280b7081-d318-4c44-b127-3126bf1b8691_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_280b7081-d318-4c44-b127-3126bf1b8691" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_280b7081-d318-4c44-b127-3126bf1b8691_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b04c3b33-7278-48d1-8f2e-81212d6f2db2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_280b7081-d318-4c44-b127-3126bf1b8691" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b04c3b33-7278-48d1-8f2e-81212d6f2db2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_39a758bb-651c-42c0-9487-1edd0aacf07a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b04c3b33-7278-48d1-8f2e-81212d6f2db2" xlink:to="loc_us-gaap_EmployeeStockMember_39a758bb-651c-42c0-9487-1edd0aacf07a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_c525d9aa-454c-4682-8fae-e49face80dd2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0df33834-898e-4581-8718-831aa8c255ba" xlink:to="loc_us-gaap_PlanNameAxis_c525d9aa-454c-4682-8fae-e49face80dd2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_c525d9aa-454c-4682-8fae-e49face80dd2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_c525d9aa-454c-4682-8fae-e49face80dd2" xlink:to="loc_us-gaap_PlanNameDomain_c525d9aa-454c-4682-8fae-e49face80dd2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_82f07fe3-02c8-4002-87c5-7c76bbbba0d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_c525d9aa-454c-4682-8fae-e49face80dd2" xlink:to="loc_us-gaap_PlanNameDomain_82f07fe3-02c8-4002-87c5-7c76bbbba0d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_EmployeeStockPurchasePlanMember_20b1fe6e-60f1-4c7c-8c3b-e6c92f3a5652" xlink:href="open-20230630.xsd#open_EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_82f07fe3-02c8-4002-87c5-7c76bbbba0d5" xlink:to="loc_open_EmployeeStockPurchasePlanMember_20b1fe6e-60f1-4c7c-8c3b-e6c92f3a5652" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_8c8fea13-02d3-4c1c-bb24-0cf88a199804" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0df33834-898e-4581-8718-831aa8c255ba" xlink:to="loc_srt_RangeAxis_8c8fea13-02d3-4c1c-bb24-0cf88a199804" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8c8fea13-02d3-4c1c-bb24-0cf88a199804_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8c8fea13-02d3-4c1c-bb24-0cf88a199804" xlink:to="loc_srt_RangeMember_8c8fea13-02d3-4c1c-bb24-0cf88a199804_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8830107f-2ec2-4c72-9f98-482f3c012e73" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8c8fea13-02d3-4c1c-bb24-0cf88a199804" xlink:to="loc_srt_RangeMember_8830107f-2ec2-4c72-9f98-482f3c012e73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_1c86ee05-6138-4470-9bb4-26e1761387dd" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8830107f-2ec2-4c72-9f98-482f3c012e73" xlink:to="loc_srt_MinimumMember_1c86ee05-6138-4470-9bb4-26e1761387dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_3994dbf5-ead1-4e5f-9522-177b7dca4b7c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8830107f-2ec2-4c72-9f98-482f3c012e73" xlink:to="loc_srt_MaximumMember_3994dbf5-ead1-4e5f-9522-177b7dca4b7c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/SHAREBASEDAWARDSExpenseandCapitalizedDetails" xlink:type="simple" xlink:href="open-20230630.xsd#SHAREBASEDAWARDSExpenseandCapitalizedDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/SHAREBASEDAWARDSExpenseandCapitalizedDetails" xlink:type="extended" id="ice9ace2094fd431e9e8d4ef832005a2a_SHAREBASEDAWARDSExpenseandCapitalizedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_63dacf5b-ba87-4e80-9065-9e181ddd4373" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_067b88bc-a041-49b7-bb5b-381c5eb86ddf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_63dacf5b-ba87-4e80-9065-9e181ddd4373" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_067b88bc-a041-49b7-bb5b-381c5eb86ddf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_16f0ad12-2725-443b-8f18-ffd3fadf263c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_63dacf5b-ba87-4e80-9065-9e181ddd4373" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_16f0ad12-2725-443b-8f18-ffd3fadf263c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_79f217f0-e970-4ac6-9e65-3f8d82cda979" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_16f0ad12-2725-443b-8f18-ffd3fadf263c" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_79f217f0-e970-4ac6-9e65-3f8d82cda979" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_79f217f0-e970-4ac6-9e65-3f8d82cda979_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_79f217f0-e970-4ac6-9e65-3f8d82cda979" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_79f217f0-e970-4ac6-9e65-3f8d82cda979_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_da1cdf9e-c00e-4d40-84ab-96d9214d79e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_79f217f0-e970-4ac6-9e65-3f8d82cda979" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_da1cdf9e-c00e-4d40-84ab-96d9214d79e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_1f08c6dd-2563-4391-8094-2421eac6468d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_da1cdf9e-c00e-4d40-84ab-96d9214d79e9" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_1f08c6dd-2563-4391-8094-2421eac6468d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_e4e9b4f9-696f-489d-8048-ffe75f5015b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_da1cdf9e-c00e-4d40-84ab-96d9214d79e9" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_e4e9b4f9-696f-489d-8048-ffe75f5015b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_ce5de363-ceb5-4809-9515-50576a588a7b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_da1cdf9e-c00e-4d40-84ab-96d9214d79e9" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_ce5de363-ceb5-4809-9515-50576a588a7b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/SHAREBASEDAWARDSStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="open-20230630.xsd#SHAREBASEDAWARDSStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/SHAREBASEDAWARDSStockBasedCompensationExpenseDetails" xlink:type="extended" id="i9aaf5af9b11449a08b03a4d3c63d0a27_SHAREBASEDAWARDSStockBasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fc0169da-9e79-4f1a-a37d-e6a6aa34715d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ShareBasedPaymentArrangementNumberOfAwardsWithSatisfiedMarketConditions_ef78513c-1bcd-4a9e-86e3-de34c087f5a1" xlink:href="open-20230630.xsd#open_ShareBasedPaymentArrangementNumberOfAwardsWithSatisfiedMarketConditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fc0169da-9e79-4f1a-a37d-e6a6aa34715d" xlink:to="loc_open_ShareBasedPaymentArrangementNumberOfAwardsWithSatisfiedMarketConditions_ef78513c-1bcd-4a9e-86e3-de34c087f5a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_6f146159-2d72-4e26-ad8f-6a90df7add32" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fc0169da-9e79-4f1a-a37d-e6a6aa34715d" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_6f146159-2d72-4e26-ad8f-6a90df7add32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c758ed90-5536-4314-a118-1eec3ac467ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fc0169da-9e79-4f1a-a37d-e6a6aa34715d" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c758ed90-5536-4314-a118-1eec3ac467ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbfc6ad9-a7ab-4298-9fc9-77df33461295" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_fc0169da-9e79-4f1a-a37d-e6a6aa34715d" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbfc6ad9-a7ab-4298-9fc9-77df33461295" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_51ef5b9d-68d1-4fee-9576-8135146699a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbfc6ad9-a7ab-4298-9fc9-77df33461295" xlink:to="loc_us-gaap_AwardTypeAxis_51ef5b9d-68d1-4fee-9576-8135146699a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_51ef5b9d-68d1-4fee-9576-8135146699a5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_51ef5b9d-68d1-4fee-9576-8135146699a5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_51ef5b9d-68d1-4fee-9576-8135146699a5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5321e2c6-edd6-45c6-afc9-9d6f2c6fbc23" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_51ef5b9d-68d1-4fee-9576-8135146699a5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5321e2c6-edd6-45c6-afc9-9d6f2c6fbc23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MarketConditionAwardMember_e53ead10-8f27-4230-b775-e476ef4f19d1" xlink:href="open-20230630.xsd#open_MarketConditionAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5321e2c6-edd6-45c6-afc9-9d6f2c6fbc23" xlink:to="loc_open_MarketConditionAwardMember_e53ead10-8f27-4230-b775-e476ef4f19d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_UnvestedStockOptionsAndRestrictedSharesMember_734efabc-08cb-4d4b-9c0c-c1948d6db9ce" xlink:href="open-20230630.xsd#open_UnvestedStockOptionsAndRestrictedSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5321e2c6-edd6-45c6-afc9-9d6f2c6fbc23" xlink:to="loc_open_UnvestedStockOptionsAndRestrictedSharesMember_734efabc-08cb-4d4b-9c0c-c1948d6db9ce" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/WARRANTSDetails" xlink:type="simple" xlink:href="open-20230630.xsd#WARRANTSDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/WARRANTSDetails" xlink:type="extended" id="ib11a6955ffd04f4eb50dd397d49b6994_WARRANTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsAuthorized_dceb0d1e-717f-4e9c-a9a0-b1a0c8430796" xlink:href="open-20230630.xsd#open_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:to="loc_open_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsAuthorized_dceb0d1e-717f-4e9c-a9a0-b1a0c8430796" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ClassOfWarrantOrRightExercisePriceVolumeWeightedAveragePriceDays_1287c23c-dd2c-4deb-b591-a42237cc8cad" xlink:href="open-20230630.xsd#open_ClassOfWarrantOrRightExercisePriceVolumeWeightedAveragePriceDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:to="loc_open_ClassOfWarrantOrRightExercisePriceVolumeWeightedAveragePriceDays_1287c23c-dd2c-4deb-b591-a42237cc8cad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_e4566a5f-ebac-48fb-8fdc-ef1a1aea80a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_e4566a5f-ebac-48fb-8fdc-ef1a1aea80a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_f917960e-d5d2-4bcc-bb73-48ffe09d5db7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_f917960e-d5d2-4bcc-bb73-48ffe09d5db7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_0b9bf0aa-4f3b-4cd1-8792-cf9b559daffd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_270d6df3-8f44-4682-b17f-765449ec87b2" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_0b9bf0aa-4f3b-4cd1-8792-cf9b559daffd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_1a4ae0ff-cf9c-485b-bc93-565d7df094c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_0b9bf0aa-4f3b-4cd1-8792-cf9b559daffd" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_1a4ae0ff-cf9c-485b-bc93-565d7df094c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_1a4ae0ff-cf9c-485b-bc93-565d7df094c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1a4ae0ff-cf9c-485b-bc93-565d7df094c0" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_1a4ae0ff-cf9c-485b-bc93-565d7df094c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_5ef231f7-bd9e-48e4-bec9-1d6204565629" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_1a4ae0ff-cf9c-485b-bc93-565d7df094c0" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_5ef231f7-bd9e-48e4-bec9-1d6204565629" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MarketingWarrantsMember_f54d2a86-309f-4a6c-9b1b-3b7e7e1d42e0" xlink:href="open-20230630.xsd#open_MarketingWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_5ef231f7-bd9e-48e4-bec9-1d6204565629" xlink:to="loc_open_MarketingWarrantsMember_f54d2a86-309f-4a6c-9b1b-3b7e7e1d42e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_cde87d32-8c26-4dcb-8c19-0da04e573ae3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_0b9bf0aa-4f3b-4cd1-8792-cf9b559daffd" xlink:to="loc_srt_CounterpartyNameAxis_cde87d32-8c26-4dcb-8c19-0da04e573ae3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cde87d32-8c26-4dcb-8c19-0da04e573ae3_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_cde87d32-8c26-4dcb-8c19-0da04e573ae3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cde87d32-8c26-4dcb-8c19-0da04e573ae3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_508fb446-e8ec-4bed-9e4c-9f56383216e9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_cde87d32-8c26-4dcb-8c19-0da04e573ae3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_508fb446-e8ec-4bed-9e4c-9f56383216e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ZillowIncMember_c79ec45b-af82-4fe2-8ce8-73432485f4e6" xlink:href="open-20230630.xsd#open_ZillowIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_508fb446-e8ec-4bed-9e4c-9f56383216e9" xlink:to="loc_open_ZillowIncMember_c79ec45b-af82-4fe2-8ce8-73432485f4e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_f46e80e5-6ac8-4e47-969b-71983fabba90" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_0b9bf0aa-4f3b-4cd1-8792-cf9b559daffd" xlink:to="loc_srt_RangeAxis_f46e80e5-6ac8-4e47-969b-71983fabba90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f46e80e5-6ac8-4e47-969b-71983fabba90_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_f46e80e5-6ac8-4e47-969b-71983fabba90" xlink:to="loc_srt_RangeMember_f46e80e5-6ac8-4e47-969b-71983fabba90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f8dc55d7-46dc-40bd-80b4-2cef713cc265" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_f46e80e5-6ac8-4e47-969b-71983fabba90" xlink:to="loc_srt_RangeMember_f8dc55d7-46dc-40bd-80b4-2cef713cc265" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_39918c22-f0b4-44c0-a469-975255de1664" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f8dc55d7-46dc-40bd-80b4-2cef713cc265" xlink:to="loc_srt_MinimumMember_39918c22-f0b4-44c0-a469-975255de1664" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_3d4b1a25-2377-4ebc-aebd-2e7eecebe518" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f8dc55d7-46dc-40bd-80b4-2cef713cc265" xlink:to="loc_srt_MaximumMember_3d4b1a25-2377-4ebc-aebd-2e7eecebe518" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/NETINCOMELOSSPERSHAREEarningsPerShareBasicandDilutedDetails" xlink:type="simple" xlink:href="open-20230630.xsd#NETINCOMELOSSPERSHAREEarningsPerShareBasicandDilutedDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/NETINCOMELOSSPERSHAREEarningsPerShareBasicandDilutedDetails" xlink:type="extended" id="i6a7932dab22f4b4496441b0aa5ca255e_NETINCOMELOSSPERSHAREEarningsPerShareBasicandDilutedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedLineItems_ae604952-f129-45e0-819e-13989d6a44c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDilutedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_6a657eee-7694-4f04-9cf1-141ffbaf4f8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_ae604952-f129-45e0-819e-13989d6a44c0" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_6a657eee-7694-4f04-9cf1-141ffbaf4f8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_eafcab91-6d61-4d20-a16a-d7048a021d25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_6a657eee-7694-4f04-9cf1-141ffbaf4f8a" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_eafcab91-6d61-4d20-a16a-d7048a021d25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_c22b12e4-3263-4417-8abf-be542a6e6dbe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_eafcab91-6d61-4d20-a16a-d7048a021d25" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_c22b12e4-3263-4417-8abf-be542a6e6dbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_37eda396-0206-4939-85e7-059b51a9fefd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_eafcab91-6d61-4d20-a16a-d7048a021d25" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_37eda396-0206-4939-85e7-059b51a9fefd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_6a657eee-7694-4f04-9cf1-141ffbaf4f8a" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_d51551d3-bc2d-4b18-bf97-900886b66d83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_d51551d3-bc2d-4b18-bf97-900886b66d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_6af78d59-f504-4206-b3ef-922aa8430ae9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_6af78d59-f504-4206-b3ef-922aa8430ae9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_f13bcd60-08e3-4a81-8561-17d209713b1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_f13bcd60-08e3-4a81-8561-17d209713b1c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_86fcec08-b451-4518-b266-cf6626eee575" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:to="loc_us-gaap_EarningsPerShareBasic_86fcec08-b451-4518-b266-cf6626eee575" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_80b411c8-85b8-412d-8f47-b3514540d0f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_574d542b-c54a-42af-b2a3-dbc7d64ec26d" xlink:to="loc_us-gaap_EarningsPerShareDiluted_80b411c8-85b8-412d-8f47-b3514540d0f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_e5eb0470-36c4-4995-a94f-35b5b2a2062e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_ae604952-f129-45e0-819e-13989d6a44c0" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_e5eb0470-36c4-4995-a94f-35b5b2a2062e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_adae1e11-ae8c-4756-9278-7ee2b37e0fc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_e5eb0470-36c4-4995-a94f-35b5b2a2062e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_adae1e11-ae8c-4756-9278-7ee2b37e0fc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_adae1e11-ae8c-4756-9278-7ee2b37e0fc3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_adae1e11-ae8c-4756-9278-7ee2b37e0fc3" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_adae1e11-ae8c-4756-9278-7ee2b37e0fc3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_bd775c24-d91e-489a-a7f8-b11876d72afd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_adae1e11-ae8c-4756-9278-7ee2b37e0fc3" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_bd775c24-d91e-489a-a7f8-b11876d72afd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_2fc00243-643c-4368-b050-596896cae3a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_bd775c24-d91e-489a-a7f8-b11876d72afd" xlink:to="loc_us-gaap_EmployeeStockMember_2fc00243-643c-4368-b050-596896cae3a7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/NETINCOMELOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="simple" xlink:href="open-20230630.xsd#NETINCOMELOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/NETINCOMELOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" xlink:type="extended" id="id8b27cc91a4d4f58a5da0939d675619e_NETINCOMELOSSPERSHAREAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_770d0659-2618-460f-85cb-a21a5b6b5338" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_cdafa01b-5150-434f-ba74-296f8407c021" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_770d0659-2618-460f-85cb-a21a5b6b5338" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_cdafa01b-5150-434f-ba74-296f8407c021" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7d372043-e5aa-4c4f-85d8-4e4dd8f8b69e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_770d0659-2618-460f-85cb-a21a5b6b5338" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7d372043-e5aa-4c4f-85d8-4e4dd8f8b69e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1ea74dd1-5c0f-4174-8133-07ca9f119b37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_7d372043-e5aa-4c4f-85d8-4e4dd8f8b69e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1ea74dd1-5c0f-4174-8133-07ca9f119b37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1ea74dd1-5c0f-4174-8133-07ca9f119b37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1ea74dd1-5c0f-4174-8133-07ca9f119b37" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1ea74dd1-5c0f-4174-8133-07ca9f119b37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1ea74dd1-5c0f-4174-8133-07ca9f119b37" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_a9f5d9c8-54c1-4275-815e-24ca775b480a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_a9f5d9c8-54c1-4275-815e-24ca775b480a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_cfdbef48-7893-47a2-8dc4-cf2f4e859574" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:to="loc_us-gaap_EmployeeStockOptionMember_cfdbef48-7893-47a2-8dc4-cf2f4e859574" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_d4a1d0f4-8ef9-40fd-96a7-4719d8cc6701" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:to="loc_us-gaap_RestrictedStockMember_d4a1d0f4-8ef9-40fd-96a7-4719d8cc6701" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_304e0247-f270-463e-93a9-e70d7ea93afd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_83d1f010-1d6d-45a1-9313-9db27b8ac437" xlink:to="loc_us-gaap_EmployeeStockMember_304e0247-f270-463e-93a9-e70d7ea93afd" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/BUSINESSACQUISITIONDetails" xlink:type="simple" xlink:href="open-20230630.xsd#BUSINESSACQUISITIONDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/BUSINESSACQUISITIONDetails" xlink:type="extended" id="iee1311949dea4817991119cdc1c1f516_BUSINESSACQUISITIONDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_32c2d2c4-96e7-4f59-b8c7-6fe1d03d3311" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_32c2d2c4-96e7-4f59-b8c7-6fe1d03d3311" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_06972d38-621f-4d7b-b8df-7a03e7d1b366" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_06972d38-621f-4d7b-b8df-7a03e7d1b366" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_51ae3fa2-78e9-432a-a4b3-ba6beb85575b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_51ae3fa2-78e9-432a-a4b3-ba6beb85575b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_fbbb1224-a521-459b-aaec-26039caf8ff0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:to="loc_us-gaap_Goodwill_fbbb1224-a521-459b-aaec-26039caf8ff0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_687a8dd9-671b-4171-b412-1b7120f5b6f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_db7986b8-92eb-4ea6-bef5-b7a12e37e2dc" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_687a8dd9-671b-4171-b412-1b7120f5b6f9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_ce524318-bf74-4239-a7db-480af7ae6f23" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_687a8dd9-671b-4171-b412-1b7120f5b6f9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_ce524318-bf74-4239-a7db-480af7ae6f23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ce524318-bf74-4239-a7db-480af7ae6f23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ce524318-bf74-4239-a7db-480af7ae6f23" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ce524318-bf74-4239-a7db-480af7ae6f23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9f594e04-6fe7-48c9-8836-cc19105c6bb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ce524318-bf74-4239-a7db-480af7ae6f23" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9f594e04-6fe7-48c9-8836-cc19105c6bb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_TaxProperMember_f50841fe-a1c5-444c-80c0-5d29313924cc" xlink:href="open-20230630.xsd#open_TaxProperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9f594e04-6fe7-48c9-8836-cc19105c6bb2" xlink:to="loc_open_TaxProperMember_f50841fe-a1c5-444c-80c0-5d29313924cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7aa41401-bdef-4940-9f3f-22b4e6217da3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_687a8dd9-671b-4171-b412-1b7120f5b6f9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7aa41401-bdef-4940-9f3f-22b4e6217da3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7aa41401-bdef-4940-9f3f-22b4e6217da3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7aa41401-bdef-4940-9f3f-22b4e6217da3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7aa41401-bdef-4940-9f3f-22b4e6217da3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1779ad21-2c04-4ef4-80c7-ca8c1f9916a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7aa41401-bdef-4940-9f3f-22b4e6217da3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1779ad21-2c04-4ef4-80c7-ca8c1f9916a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_0ea4bbe1-1993-4a25-ae21-6fe591318e03" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1779ad21-2c04-4ef4-80c7-ca8c1f9916a1" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_0ea4bbe1-1993-4a25-ae21-6fe591318e03" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://opendoor.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="open-20230630.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
  <link:definitionLink xlink:role="http://opendoor.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended" id="i7a5d1bf649a24fedbef97c39d32ae6a0_COMMITMENTSANDCONTINGENCIESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_LesseeOperatingLeaseLiabilityToBePaidDecrease_f127f80f-40c0-4577-8686-bfe8f8a5c27e" xlink:href="open-20230630.xsd#open_LesseeOperatingLeaseLiabilityToBePaidDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:to="loc_open_LesseeOperatingLeaseLiabilityToBePaidDecrease_f127f80f-40c0-4577-8686-bfe8f8a5c27e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_d9310ced-f020-4e33-98c4-c7349afade22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_d9310ced-f020-4e33-98c4-c7349afade22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_IncreaseDecreaseInOperatingLeaseRightOfUseAsset_47b41001-f7eb-4bb2-9a5a-4c20c03acebf" xlink:href="open-20230630.xsd#open_IncreaseDecreaseInOperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:to="loc_open_IncreaseDecreaseInOperatingLeaseRightOfUseAsset_47b41001-f7eb-4bb2-9a5a-4c20c03acebf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnTerminationOfLease_5cc411f7-d1f4-45dd-a611-6742198e9184" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnTerminationOfLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:to="loc_us-gaap_GainLossOnTerminationOfLease_5cc411f7-d1f4-45dd-a611-6742198e9184" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_ff5e3bec-7420-4767-9b08-b6468934aa3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_94ce040b-3eea-42d5-aee4-1cf0cb0c57cf" xlink:to="loc_us-gaap_OtherCommitmentsTable_ff5e3bec-7420-4767-9b08-b6468934aa3f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_8744669d-902c-4b83-bd69-9c8ce6290fc4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_ff5e3bec-7420-4767-9b08-b6468934aa3f" xlink:to="loc_srt_StatementGeographicalAxis_8744669d-902c-4b83-bd69-9c8ce6290fc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_8744669d-902c-4b83-bd69-9c8ce6290fc4_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_8744669d-902c-4b83-bd69-9c8ce6290fc4" xlink:to="loc_srt_SegmentGeographicalDomain_8744669d-902c-4b83-bd69-9c8ce6290fc4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_f744ebf8-5068-4a13-89f1-4c564b29ac24" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_8744669d-902c-4b83-bd69-9c8ce6290fc4" xlink:to="loc_srt_SegmentGeographicalDomain_f744ebf8-5068-4a13-89f1-4c564b29ac24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ArizonaOfficeLeaseMember_623faacd-c820-478a-8889-8ba31d3bb142" xlink:href="open-20230630.xsd#open_ArizonaOfficeLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_f744ebf8-5068-4a13-89f1-4c564b29ac24" xlink:to="loc_open_ArizonaOfficeLeaseMember_623faacd-c820-478a-8889-8ba31d3bb142" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-roles-2023.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockMember" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_EmployeeStockMember" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MarketConditionAwardMember_e9925bc0-198c-4cf9-a35e-6c4288d9abec" xlink:href="open-20230630.xsd#open_MarketConditionAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_open_MarketConditionAwardMember_e9925bc0-198c-4cf9-a35e-6c4288d9abec" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_UnvestedStockOptionsAndRestrictedSharesMember_193bbf75-ccf2-42b1-bfab-3b8427983144" xlink:href="open-20230630.xsd#open_UnvestedStockOptionsAndRestrictedSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_open_UnvestedStockOptionsAndRestrictedSharesMember_193bbf75-ccf2-42b1-bfab-3b8427983144" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_MeganMeyerMember_ccbf588e-849c-44c0-b969-fbd19c29ee6f" xlink:href="open-20230630.xsd#open_MeganMeyerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_open_MeganMeyerMember_ccbf588e-849c-44c0-b969-fbd19c29ee6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_open_ChristinaSchwartzMember_3151d659-53f3-4aeb-aa2c-6140c603fb88" xlink:href="open-20230630.xsd#open_ChristinaSchwartzMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_open_ChristinaSchwartzMember_3151d659-53f3-4aeb-aa2c-6140c603fb88" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
