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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019caf13-6435-7584-a10f-5327949649ee,g:8cab3730-8362-4704-af53-fcd38ff27875-->
<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://www.ally.com/role/CondensedConsolidatedBalanceSheetunauditedVIEs" xlink:type="simple" xlink:href="ally-20260331.xsd#CondensedConsolidatedBalanceSheetunauditedVIEs"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/CondensedConsolidatedBalanceSheetunauditedVIEs" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019caf13-7024-7262-a82e-3d920f6237f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_StatementTable_019caf13-7024-7262-a82e-3d920f6237f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019caf13-7024-7b68-9e03-caf4dd853c56" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf13-7024-7262-a82e-3d920f6237f2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019caf13-7024-7b68-9e03-caf4dd853c56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-7024-7b68-9e03-caf4dd853c56_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-7024-7b68-9e03-caf4dd853c56" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-7024-7b68-9e03-caf4dd853c56_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-7024-76e9-9657-6fb65424e512" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-7024-7b68-9e03-caf4dd853c56" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-7024-76e9-9657-6fb65424e512" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019caf13-7024-74e8-a4c9-c2d996828e1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019caf13-7024-76e9-9657-6fb65424e512" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019caf13-7024-74e8-a4c9-c2d996828e1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7024-76a6-93bf-9147662c31c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf13-7024-7262-a82e-3d920f6237f2" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7024-76a6-93bf-9147662c31c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7024-76a6-93bf-9147662c31c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7024-76a6-93bf-9147662c31c1" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7024-76a6-93bf-9147662c31c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7024-76bb-b230-428fa6d7e932" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7024-76a6-93bf-9147662c31c1" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7024-76bb-b230-428fa6d7e932" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-7024-7800-87d2-327bcf446c5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7024-76bb-b230-428fa6d7e932" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-7024-7800-87d2-327bcf446c5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7024-7c14-8ba0-07ec9436121b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf13-7024-7262-a82e-3d920f6237f2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7024-7c14-8ba0-07ec9436121b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7024-7c14-8ba0-07ec9436121b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7024-7c14-8ba0-07ec9436121b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7024-7c14-8ba0-07ec9436121b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7024-7329-87ec-db33d54b06bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7024-7c14-8ba0-07ec9436121b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7024-7329-87ec-db33d54b06bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-7024-725d-ae9a-f5f32bd67bac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7024-7329-87ec-db33d54b06bd" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-7024-725d-ae9a-f5f32bd67bac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-7024-79fa-bf54-359b21d09cc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-7024-79fa-bf54-359b21d09cc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019caf13-7024-7683-8737-f976f1c323ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019caf13-7024-7683-8737-f976f1c323ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7024-7de3-b5ca-539ddf8001b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7024-7de3-b5ca-539ddf8001b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019caf13-7024-7a93-8b7e-5854f598e586" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_OtherAssets_019caf13-7024-7a93-8b7e-5854f598e586" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019caf13-7024-790f-bcf6-2b07644782f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_Assets_019caf13-7024-790f-bcf6-2b07644782f3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019caf13-7024-761e-bf7b-6879da6b6d82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_LongTermDebt_019caf13-7024-761e-bf7b-6879da6b6d82" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_019caf13-7024-7273-b408-a3d3c4b4fffa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_019caf13-7024-7273-b408-a3d3c4b4fffa" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019caf13-7024-706c-9054-e044232b7918" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7586-bd37-d330ef24db98" xlink:to="loc_us-gaap_Liabilities_019caf13-7024-706c-9054-e044232b7918" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/CondensedConsolidatedStatementofChangesinEquityunaudited" xlink:type="simple" xlink:href="ally-20260331.xsd#CondensedConsolidatedStatementofChangesinEquityunaudited"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/CondensedConsolidatedStatementofChangesinEquityunaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019caf13-7024-7ad8-a3ae-57e29df80ec5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019caf13-7024-79e4-8aca-6a97f435ae62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7ad8-a3ae-57e29df80ec5" xlink:to="loc_us-gaap_StatementTable_019caf13-7024-79e4-8aca-6a97f435ae62" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7024-758e-9146-b77034365606" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf13-7024-79e4-8aca-6a97f435ae62" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7024-758e-9146-b77034365606" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7024-758e-9146-b77034365606_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7024-758e-9146-b77034365606" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7024-758e-9146-b77034365606_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7024-758e-9146-b77034365606" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember_019caf13-7024-77bd-b85b-d3e3610537b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:to="loc_us-gaap_CommonStockIncludingAdditionalPaidInCapitalMember_019caf13-7024-77bd-b85b-d3e3610537b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019caf13-7024-729b-8a68-a05435e28fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:to="loc_us-gaap_PreferredStockMember_019caf13-7024-729b-8a68-a05435e28fdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019caf13-7024-7496-b03b-31df6d954f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:to="loc_us-gaap_RetainedEarningsMember_019caf13-7024-7496-b03b-31df6d954f1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7024-7f02-b311-d5a3337ac6ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7024-7f02-b311-d5a3337ac6ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019caf13-7024-7670-bb8a-97bfae360b26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7024-7510-93b2-2603ef3510fd" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019caf13-7024-7670-bb8a-97bfae360b26" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019caf13-7024-7d9b-b62a-575e7b4f4496" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf13-7024-79e4-8aca-6a97f435ae62" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019caf13-7024-7d9b-b62a-575e7b4f4496" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7024-7d9b-b62a-575e7b4f4496_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7024-7d9b-b62a-575e7b4f4496" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7024-7d9b-b62a-575e7b4f4496_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7024-74c0-8bf7-4fab64daed96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7024-7d9b-b62a-575e7b4f4496" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7024-74c0-8bf7-4fab64daed96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7024-7e75-b653-cae274304497" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7024-74c0-8bf7-4fab64daed96" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7024-7e75-b653-cae274304497" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7024-7d56-a83e-a2392daeb396" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesCPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7024-74c0-8bf7-4fab64daed96" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7024-7d56-a83e-a2392daeb396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf13-7024-7ad8-a3ae-57e29df80ec5" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019caf13-7024-7f6b-b3ce-deafa8e798d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_StockholdersEquity_019caf13-7024-7f6b-b3ce-deafa8e798d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019caf13-7024-7f81-aa89-44027136bbbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_NetIncomeLoss_019caf13-7024-7f81-aa89-44027136bbbc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPreferredStockCash_019caf13-7024-7206-80af-15b64c315855" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsPreferredStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_DividendsPreferredStockCash_019caf13-7024-7206-80af-15b64c315855" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019caf13-7024-74a8-9279-932d02337159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019caf13-7024-74a8-9279-932d02337159" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7024-7e4b-b1f3-c2d491bcb3da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7024-7e4b-b1f3-c2d491bcb3da" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019caf13-7024-7a1c-a7e4-aefc0160d8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019caf13-7024-7a1c-a7e4-aefc0160d8f0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019caf13-7024-7048-8026-1c714f3412ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf13-7024-7626-bcf3-558a787621d6" xlink:to="loc_us-gaap_DividendsCommonStockCash_019caf13-7024-7048-8026-1c714f3412ef" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019caf13-7024-7d26-aa0a-06adc6abc524" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/RevenuefromContractswithCustomersDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#RevenuefromContractswithCustomersDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/RevenuefromContractswithCustomersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7024-7221-9b9c-dabc4dbe7816_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7024-7221-9b9c-dabc4dbe7816_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf13-7024-7c5d-af7a-44cdd55d4a92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf13-7024-7c5d-af7a-44cdd55d4a92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7024-73e5-9471-424d810438c0" xlink:href="ally-20260331.xsd#ally_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:to="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7024-73e5-9471-424d810438c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019caf13-7024-73ba-91d1-7f70d4a98355_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:to="loc_srt_ProductsAndServicesDomain_019caf13-7024-73ba-91d1-7f70d4a98355_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:to="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_NoninsuranceContractsMember_019caf13-7024-7db9-92c9-eea45555f852" xlink:href="ally-20260331.xsd#ally_NoninsuranceContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_NoninsuranceContractsMember_019caf13-7024-7db9-92c9-eea45555f852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_RemarketingActivitiesMember_019caf13-7024-7152-9381-988dec3c0a6e" xlink:href="ally-20260331.xsd#ally_RemarketingActivitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_RemarketingActivitiesMember_019caf13-7024-7152-9381-988dec3c0a6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BrokerageCommissionsandOtherMember_019caf13-7024-7403-b8b9-4b3b560dff14" xlink:href="ally-20260331.xsd#ally_BrokerageCommissionsandOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BrokerageCommissionsandOtherMember_019caf13-7024-7403-b8b9-4b3b560dff14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BankingFeesAndInterchangeIncomeMember_019caf13-7024-788d-86c6-c86ecb7082cf" xlink:href="ally-20260331.xsd#ally_BankingFeesAndInterchangeIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BankingFeesAndInterchangeIncomeMember_019caf13-7024-788d-86c6-c86ecb7082cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BrokeredAgentCommissionsMember_019caf13-7024-769c-82ff-9aa9bbd8ad6c" xlink:href="ally-20260331.xsd#ally_BrokeredAgentCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BrokeredAgentCommissionsMember_019caf13-7024-769c-82ff-9aa9bbd8ad6c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019caf13-7024-794a-a3ed-f45d8136f8b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019caf13-7024-794a-a3ed-f45d8136f8b3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7024-78c0-b343-c7c5e09d99e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7024-78c0-b343-c7c5e09d99e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7024-783c-a239-674317ca6aea" xlink:href="ally-20260331.xsd#ally_AutomotiveFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7024-783c-a239-674317ca6aea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InsuranceOperationsSegmentMember_019caf13-7024-7fb6-b419-a2f4c4fd38e2" xlink:href="ally-20260331.xsd#ally_InsuranceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_InsuranceOperationsSegmentMember_019caf13-7024-7fb6-b419-a2f4c4fd38e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7024-7929-939a-cbf35e1d2472" xlink:href="ally-20260331.xsd#ally_CorporateFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7024-7929-939a-cbf35e1d2472" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019caf13-7024-7e95-8a78-69abafa7c103" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019caf13-7024-7e95-8a78-69abafa7c103" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf13-7024-7950-9c3c-fbd38b588e0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf13-7024-7950-9c3c-fbd38b588e0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomerOther_019caf13-7024-70e8-a44f-d15e70682b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueNotFromContractWithCustomerOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomerOther_019caf13-7024-70e8-a44f-d15e70682b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019caf13-7024-765d-91eb-6a5553a8bbbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_NoninterestIncome_019caf13-7024-765d-91eb-6a5553a8bbbe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019caf13-7024-731e-92bd-ab7f77623f8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019caf13-7024-731e-92bd-ab7f77623f8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019caf13-7024-76de-8784-0652e3fe3757" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019caf13-7024-76de-8784-0652e3fe3757" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019caf13-7024-777a-9dda-39ee4699258f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019caf13-7024-777a-9dda-39ee4699258f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_019caf13-7024-7c36-929e-6b2c659dc9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_CapitalizedContractCostNet_019caf13-7024-7c36-929e-6b2c659dc9bc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_019caf13-7024-7f42-ab83-a599aa5cd00d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_019caf13-7024-7f42-ab83-a599aa5cd00d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CustomerRewardsExpense_019caf13-7024-7647-b8d2-96215144ef98" xlink:href="ally-20260331.xsd#ally_CustomerRewardsExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_ally_CustomerRewardsExpense_019caf13-7024-7647-b8d2-96215144ef98" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_RemarketingGainsLossesNet_019caf13-7024-73f7-9aba-ca75af1f3428" xlink:href="ally-20260331.xsd#ally_RemarketingGainsLossesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_ally_RemarketingGainsLossesNet_019caf13-7024-73f7-9aba-ca75af1f3428" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/RevenuefromContractswithCustomersDetails_1" xlink:type="simple" xlink:href="ally-20260331.xsd#RevenuefromContractswithCustomersDetails_1"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/RevenuefromContractswithCustomersDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7024-7221-9b9c-dabc4dbe7816_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7024-7221-9b9c-dabc4dbe7816_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7024-7221-9b9c-dabc4dbe7816" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf13-7024-7c5d-af7a-44cdd55d4a92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf13-7024-7c5d-af7a-44cdd55d4a92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7024-73e5-9471-424d810438c0" xlink:href="ally-20260331.xsd#ally_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7024-7ffb-a84c-bfc093f290b3" xlink:to="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7024-73e5-9471-424d810438c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019caf13-7024-73ba-91d1-7f70d4a98355_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:to="loc_srt_ProductsAndServicesDomain_019caf13-7024-73ba-91d1-7f70d4a98355_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019caf13-7024-73ba-91d1-7f70d4a98355" xlink:to="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_NoninsuranceContractsMember_019caf13-7024-7db9-92c9-eea45555f852" xlink:href="ally-20260331.xsd#ally_NoninsuranceContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_NoninsuranceContractsMember_019caf13-7024-7db9-92c9-eea45555f852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_RemarketingActivitiesMember_019caf13-7024-7152-9381-988dec3c0a6e" xlink:href="ally-20260331.xsd#ally_RemarketingActivitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_RemarketingActivitiesMember_019caf13-7024-7152-9381-988dec3c0a6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BrokerageCommissionsandOtherMember_019caf13-7024-7403-b8b9-4b3b560dff14" xlink:href="ally-20260331.xsd#ally_BrokerageCommissionsandOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BrokerageCommissionsandOtherMember_019caf13-7024-7403-b8b9-4b3b560dff14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BankingFeesAndInterchangeIncomeMember_019caf13-7024-788d-86c6-c86ecb7082cf" xlink:href="ally-20260331.xsd#ally_BankingFeesAndInterchangeIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BankingFeesAndInterchangeIncomeMember_019caf13-7024-788d-86c6-c86ecb7082cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BrokeredAgentCommissionsMember_019caf13-7024-769c-82ff-9aa9bbd8ad6c" xlink:href="ally-20260331.xsd#ally_BrokeredAgentCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_ally_BrokeredAgentCommissionsMember_019caf13-7024-769c-82ff-9aa9bbd8ad6c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019caf13-7024-794a-a3ed-f45d8136f8b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019caf13-7024-7c92-92d8-dc6874267691" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019caf13-7024-794a-a3ed-f45d8136f8b3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf13-7024-770a-9a7f-87fe386a56c1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7024-78c0-b343-c7c5e09d99e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7024-78c0-b343-c7c5e09d99e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7024-78c0-b343-c7c5e09d99e3" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7024-783c-a239-674317ca6aea" xlink:href="ally-20260331.xsd#ally_AutomotiveFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7024-783c-a239-674317ca6aea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InsuranceOperationsSegmentMember_019caf13-7024-7fb6-b419-a2f4c4fd38e2" xlink:href="ally-20260331.xsd#ally_InsuranceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_InsuranceOperationsSegmentMember_019caf13-7024-7fb6-b419-a2f4c4fd38e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7024-7929-939a-cbf35e1d2472" xlink:href="ally-20260331.xsd#ally_CorporateFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7024-7031-8121-561e8c919f9c" xlink:to="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7024-7929-939a-cbf35e1d2472" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf13-7024-7950-9c3c-fbd38b588e0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf13-7024-7950-9c3c-fbd38b588e0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomerOther_019caf13-7024-70e8-a44f-d15e70682b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueNotFromContractWithCustomerOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomerOther_019caf13-7024-70e8-a44f-d15e70682b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019caf13-7024-765d-91eb-6a5553a8bbbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_NoninterestIncome_019caf13-7024-765d-91eb-6a5553a8bbbe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019caf13-7024-731e-92bd-ab7f77623f8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019caf13-7024-731e-92bd-ab7f77623f8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019caf13-7024-76de-8784-0652e3fe3757" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019caf13-7024-76de-8784-0652e3fe3757" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019caf13-7024-777a-9dda-39ee4699258f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019caf13-7024-777a-9dda-39ee4699258f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_019caf13-7024-7c36-929e-6b2c659dc9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_CapitalizedContractCostNet_019caf13-7024-7c36-929e-6b2c659dc9bc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortization_019caf13-7024-7f42-ab83-a599aa5cd00d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_us-gaap_CapitalizedContractCostAmortization_019caf13-7024-7f42-ab83-a599aa5cd00d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CustomerRewardsExpense_019caf13-7024-7647-b8d2-96215144ef98" xlink:href="ally-20260331.xsd#ally_CustomerRewardsExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_ally_CustomerRewardsExpense_019caf13-7024-7647-b8d2-96215144ef98" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_RemarketingGainsLossesNet_019caf13-7024-73f7-9aba-ca75af1f3428" xlink:href="ally-20260331.xsd#ally_RemarketingGainsLossesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf13-7024-7543-8f0b-84552ed104b2" xlink:to="loc_ally_RemarketingGainsLossesNet_019caf13-7024-73f7-9aba-ca75af1f3428" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/InvestmentSecuritiesScheduleofInvestmentPortfolioDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#InvestmentSecuritiesScheduleofInvestmentPortfolioDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/InvestmentSecuritiesScheduleofInvestmentPortfolioDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-72d7-8982-a750e8a90ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-72d7-8982-a750e8a90ee3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-72d7-8982-a750e8a90ee3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-72d7-8982-a750e8a90ee3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-72d7-8982-a750e8a90ee3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-72d7-8982-a750e8a90ee3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7025-7094-b6f4-a8120fc5ed4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7025-7094-b6f4-a8120fc5ed4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7025-73f4-a8a7-915475ad9bbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7025-73f4-a8a7-915475ad9bbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7025-7c47-bd64-712e9a8839af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7025-7c47-bd64-712e9a8839af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7025-7efb-a436-91a34a21ae22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7025-7efb-a436-91a34a21ae22" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7025-7286-b419-e47cfb3f5fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7025-7286-b419-e47cfb3f5fe4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7025-7aa3-80a5-1ef50cdc6886" xlink:href="ally-20260331.xsd#ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7025-7aa3-80a5-1ef50cdc6886" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7025-7c3e-b1b5-a6facdd362c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7025-7c3e-b1b5-a6facdd362c1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7025-7fd4-933a-9b82b529690d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7e7a-a4ff-0d9011b5ebc0" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7025-7fd4-933a-9b82b529690d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_019caf13-7025-7529-98d2-b008dfb9c5cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:to="loc_us-gaap_PledgedStatusAxis_019caf13-7025-7529-98d2-b008dfb9c5cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019caf13-7025-7529-98d2-b008dfb9c5cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_019caf13-7025-7529-98d2-b008dfb9c5cd" xlink:to="loc_us-gaap_PledgedStatusDomain_019caf13-7025-7529-98d2-b008dfb9c5cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019caf13-7025-7017-94c1-d87597bb17f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_019caf13-7025-7529-98d2-b008dfb9c5cd" xlink:to="loc_us-gaap_PledgedStatusDomain_019caf13-7025-7017-94c1-d87597bb17f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_019caf13-7025-796c-8c68-4e1e5ccc157e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetPledgedAsCollateralWithRightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_019caf13-7025-7017-94c1-d87597bb17f0" xlink:to="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_019caf13-7025-796c-8c68-4e1e5ccc157e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeAxis_019caf13-7025-7900-9d4b-edc183abdcba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:to="loc_us-gaap_PledgingPurposeAxis_019caf13-7025-7900-9d4b-edc183abdcba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_019caf13-7025-7900-9d4b-edc183abdcba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgingPurposeAxis_019caf13-7025-7900-9d4b-edc183abdcba" xlink:to="loc_us-gaap_PledgingPurposeDomain_019caf13-7025-7900-9d4b-edc183abdcba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_019caf13-7025-7f4b-ba35-e07e017d6b54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgingPurposeAxis_019caf13-7025-7900-9d4b-edc183abdcba" xlink:to="loc_us-gaap_PledgingPurposeDomain_019caf13-7025-7f4b-ba35-e07e017d6b54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019caf13-7025-79dc-9584-85718a604c03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_019caf13-7025-7f4b-ba35-e07e017d6b54" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019caf13-7025-79dc-9584-85718a604c03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-7025-70b1-8152-4a88ee9e8877" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-7025-70b1-8152-4a88ee9e8877" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7025-70b1-8152-4a88ee9e8877_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7025-70b1-8152-4a88ee9e8877" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7025-70b1-8152-4a88ee9e8877_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7025-75a3-a267-12af87b7461c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7025-70b1-8152-4a88ee9e8877" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7025-75a3-a267-12af87b7461c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf13-7025-75d8-ad1f-dedcde1d8ed0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7025-75a3-a267-12af87b7461c" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf13-7025-75d8-ad1f-dedcde1d8ed0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7025-767e-a59a-60ba65de28a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7f91-935c-7310e66cebb7" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7025-767e-a59a-60ba65de28a4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7025-767e-a59a-60ba65de28a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7025-767e-a59a-60ba65de28a4" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7025-767e-a59a-60ba65de28a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7025-7e41-890c-c959379a774c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7025-767e-a59a-60ba65de28a4" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7025-7e41-890c-c959379a774c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InsuranceOperationsSegmentMember_019caf13-7025-7a7e-be5d-ec4b17eb765d" xlink:href="ally-20260331.xsd#ally_InsuranceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7025-7e41-890c-c959379a774c" xlink:to="loc_ally_InsuranceOperationsSegmentMember_019caf13-7025-7a7e-be5d-ec4b17eb765d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7978-afe5-0e8c47bf5e37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7978-afe5-0e8c47bf5e37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019caf13-7025-70f9-b075-2346be5cadda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019caf13-7025-70f9-b075-2346be5cadda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019caf13-7025-7cc0-865d-2a983ba9c77c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019caf13-7025-7cc0-865d-2a983ba9c77c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7025-7267-a053-e96d926643da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7e3b-8ea0-d2f93a89d5c8" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7025-7267-a053-e96d926643da" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesClassifiedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7057-83fb-30810864b452" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7057-83fb-30810864b452" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019caf13-7025-7248-8f54-72e4fca6e7cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019caf13-7025-7248-8f54-72e4fca6e7cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019caf13-7025-7fac-813a-795eede54b75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019caf13-7025-7fac-813a-795eede54b75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019caf13-7025-796a-bc21-2de41081c34b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7cc3-b055-c966f7f71ddd" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019caf13-7025-796a-bc21-2de41081c34b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-7025-7e49-b21d-47e0a83459f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-7025-7e49-b21d-47e0a83459f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-7025-75f6-a5f1-e99520322748" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-7025-75f6-a5f1-e99520322748" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositAssets_019caf13-7025-7096-8402-8bd3e732a9c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DepositAssets_019caf13-7025-7096-8402-8bd3e732a9c4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndPledgedAsCollateralAssociatedLiabilitiesFairValue_019caf13-7025-7fa6-bb6a-e75cbb233d0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecurityOwnedAndPledgedAsCollateralAssociatedLiabilitiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_SecurityOwnedAndPledgedAsCollateralAssociatedLiabilitiesFairValue_019caf13-7025-7fa6-bb6a-e75cbb233d0d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-72f9-a6e5-0eb74bc0ed52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-72f9-a6e5-0eb74bc0ed52" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList_019caf13-7025-7cc0-8977-cf9333baada6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList_019caf13-7025-7cc0-8977-cf9333baada6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019caf13-7025-7e22-8584-832f68cd8376" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019caf13-7025-7e22-8584-832f68cd8376" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest_019caf13-7025-7646-b3c4-9a57201fa085" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest_019caf13-7025-7646-b3c4-9a57201fa085" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAccruedInterestBeforeAllowanceForCreditLoss_019caf13-7025-7c6e-aa30-d2d39d97ba1d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7b86-b576-7c161b748f62" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAccruedInterestBeforeAllowanceForCreditLoss_019caf13-7025-7c6e-aa30-d2d39d97ba1d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/InvestmentSecuritiesScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#InvestmentSecuritiesScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/InvestmentSecuritiesScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7d72-b911-b428859f7b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7d72-b911-b428859f7b3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-751b-bdd2-14bc60002159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentsTable_019caf13-7025-7d72-b911-b428859f7b3b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-751b-bdd2-14bc60002159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-751b-bdd2-14bc60002159_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-751b-bdd2-14bc60002159" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-751b-bdd2-14bc60002159_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7025-751b-bdd2-14bc60002159" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7025-7141-ae95-ed775b90c5b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7025-7141-ae95-ed775b90c5b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7025-7917-a845-16145a58fbef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7025-7917-a845-16145a58fbef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7025-7523-8bc5-e26c60a820e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7025-7523-8bc5-e26c60a820e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7025-7bc7-8b43-27731b4c6398" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7025-7bc7-8b43-27731b4c6398" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7025-7db6-a495-ba975331240d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7025-7db6-a495-ba975331240d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7025-79a5-87e2-ef24934d47be" xlink:href="ally-20260331.xsd#ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7025-79a5-87e2-ef24934d47be" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7025-7b24-8014-b74f8587f8c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7025-7b24-8014-b74f8587f8c3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7025-7977-a13c-95891ff5325d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7025-7617-8fdc-335ee15bb5b1" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7025-7977-a13c-95891ff5325d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7586-b5d1-87a1f1c394c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7586-b5d1-87a1f1c394c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7586-b5d1-87a1f1c394c0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7025-7a26-ae98-2e6a275542dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7025-7a26-ae98-2e6a275542dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019caf13-7025-768d-b06b-45807713c867" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019caf13-7025-768d-b06b-45807713c867" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019caf13-7025-7f18-9536-8bbcf9dd8bd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019caf13-7025-7f18-9536-8bbcf9dd8bd3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_019caf13-7025-75f6-8f45-4a5236ef29c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_019caf13-7025-75f6-8f45-4a5236ef29c8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_019caf13-7025-7596-84aa-fea3b5ae32bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAbstract_019caf13-7025-77f6-b7cb-92730393e21b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_019caf13-7025-7596-84aa-fea3b5ae32bf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7586-b5d1-87a1f1c394c0" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesAvailableForSaleExcludingAccruedInterestYield_019caf13-7025-765a-8b56-7fe739eba43f" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesAvailableForSaleExcludingAccruedInterestYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:to="loc_ally_DebtSecuritiesAvailableForSaleExcludingAccruedInterestYield_019caf13-7025-765a-8b56-7fe739eba43f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingWithinOneYearWeightedAverageYield_019caf13-7025-7a01-81d0-5dc67bf0edbb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingWithinOneYearWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingWithinOneYearWeightedAverageYield_019caf13-7025-7a01-81d0-5dc67bf0edbb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield_019caf13-7025-7c1c-a21b-9af2445d60d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield_019caf13-7025-7c1c-a21b-9af2445d60d6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield_019caf13-7025-71a1-83c0-08dac7d5b6d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield_019caf13-7025-71a1-83c0-08dac7d5b6d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfter10YearsWeightedAverageYield_019caf13-7025-7306-8351-e91dbb4f140b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfter10YearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleRollingMaturityWeightedAverageYieldAbstract_019caf13-7025-705f-8a1f-4fe666fae8f3" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleMaturityRollingAfter10YearsWeightedAverageYield_019caf13-7025-7306-8351-e91dbb4f140b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_019caf13-7025-7586-b5d1-87a1f1c394c0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7b89-b94c-26f259f15d7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7b89-b94c-26f259f15d7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019caf13-7025-734d-b54a-1eff394328d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019caf13-7025-734d-b54a-1eff394328d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019caf13-7025-7641-aac2-feabdfb531f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019caf13-7025-7641-aac2-feabdfb531f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_019caf13-7025-796d-8d93-edf0441580e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_019caf13-7025-796d-8d93-edf0441580e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_019caf13-7025-7899-a1c4-baaa7a785665" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019caf13-7025-7613-9ad5-51db238ce71b" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_019caf13-7025-7899-a1c4-baaa7a785665" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7a44-bf31-785db07cbdd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesClassifiedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7a44-bf31-785db07cbdd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7a44-bf31-785db07cbdd3" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7556-bce7-e595fa55a13b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7025-7556-bce7-e595fa55a13b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost_019caf13-7025-702a-9e04-87c7dfea932a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost_019caf13-7025-702a-9e04-87c7dfea932a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost_019caf13-7025-75ad-aad4-36450158c336" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost_019caf13-7025-75ad-aad4-36450158c336" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost_019caf13-7025-7f05-915b-e20e30231be5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost_019caf13-7025-7f05-915b-e20e30231be5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost_019caf13-70d0-7e6e-8611-8882bb90c04b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossAbstract_019caf13-7025-7de6-a16f-d0d7aea2ca4f" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost_019caf13-70d0-7e6e-8611-8882bb90c04b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019caf13-7025-7a44-bf31-785db07cbdd3" xlink:to="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYield_019caf13-70d0-7142-b878-323ddd356c0b" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:to="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYield_019caf13-70d0-7142-b878-323ddd356c0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingWithinOneYearWeightedAverageYield_019caf13-70d0-7087-a00e-d39b8a386cda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingWithinOneYearWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingWithinOneYearWeightedAverageYield_019caf13-70d0-7087-a00e-d39b8a386cda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield_019caf13-70d0-7b41-b311-b112a07f0b9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterOneThroughFiveYearsWeightedAverageYield_019caf13-70d0-7b41-b311-b112a07f0b9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield_019caf13-70d0-75a5-923a-948382a2aeaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterFiveThroughTenYearsWeightedAverageYield_019caf13-70d0-75a5-923a-948382a2aeaa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield_019caf13-70d0-76cf-ae46-58081f71c68f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLossYieldAbstract_019caf13-70d0-7ffe-96b1-ce1be225cbad" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityMaturityRollingAfterTenYearsWeightedAverageYield_019caf13-70d0-76cf-ae46-58081f71c68f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-70d0-7b4b-838a-545a3c2614d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-70d0-7b4b-838a-545a3c2614d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-70d0-7c67-95f5-969ada3c2ef2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-70d0-7c67-95f5-969ada3c2ef2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsAtCarryingValue_019caf13-70d0-7f90-9ab8-eb23dcd9346a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_CashEquivalentsAtCarryingValue_019caf13-70d0-7f90-9ab8-eb23dcd9346a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeSecuritiesTaxable_019d0158-320e-798e-96b7-a4c298911383" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeSecuritiesTaxable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_InterestIncomeSecuritiesTaxable_019d0158-320e-798e-96b7-a4c298911383" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendIncomeSecuritiesOperatingTaxable_019d0158-320e-7985-9684-0c30e27f0f4e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendIncomeSecuritiesOperatingTaxable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_DividendIncomeSecuritiesOperatingTaxable_019d0158-320e-7985-9684-0c30e27f0f4e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeSecuritiesStateAndMunicipal_019d0158-320e-7f8d-8163-f9aa1850e635" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeSecuritiesStateAndMunicipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_InterestIncomeSecuritiesStateAndMunicipal_019d0158-320e-7f8d-8163-f9aa1850e635" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDividendIncomeSecurities_019d0158-320e-7334-bb3b-74456a61e326" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestAndDividendIncomeSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019caf13-7025-7583-94c6-42d366a16f16" xlink:to="loc_us-gaap_InterestAndDividendIncomeSecurities_019d0158-320e-7334-bb3b-74456a61e326" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/InvestmentsecuritiesScheduleofInvestmentsClassifiedbyCreditRatingDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#InvestmentsecuritiesScheduleofInvestmentsClassifiedbyCreditRatingDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/InvestmentsecuritiesScheduleofInvestmentsClassifiedbyCreditRatingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019caf13-70d0-7ef2-b3c5-406688d6b841" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019caf13-70d0-7bbd-be2e-180b4fccac46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019caf13-70d0-7ef2-b3c5-406688d6b841" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019caf13-70d0-7bbd-be2e-180b4fccac46" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingFitchAxis_019caf13-70d0-7faf-974a-10a8e8f3fc9d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CreditRatingFitchAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019caf13-70d0-7bbd-be2e-180b4fccac46" xlink:to="loc_srt_CreditRatingFitchAxis_019caf13-70d0-7faf-974a-10a8e8f3fc9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-7faf-974a-10a8e8f3fc9d_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ExternalCreditRatingFitchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingFitchAxis_019caf13-70d0-7faf-974a-10a8e8f3fc9d" xlink:to="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-7faf-974a-10a8e8f3fc9d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ExternalCreditRatingFitchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingFitchAxis_019caf13-70d0-7faf-974a-10a8e8f3fc9d" xlink:to="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FitchAAARatingMember_019caf13-70d0-78b1-82f4-c7cf96973010" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FitchAAARatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:to="loc_srt_FitchAAARatingMember_019caf13-70d0-78b1-82f4-c7cf96973010" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FitchAARatingMember_019caf13-70d0-7367-8c72-a614068e5f12" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FitchAARatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:to="loc_srt_FitchAARatingMember_019caf13-70d0-7367-8c72-a614068e5f12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FitchARatingMember_019caf13-70d0-71da-87cf-7801e9d1522e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FitchARatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:to="loc_srt_FitchARatingMember_019caf13-70d0-71da-87cf-7801e9d1522e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FitchBBBRatingMember_019caf13-70d0-7475-9b23-c3e23eef4271" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FitchBBBRatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingFitchMember_019caf13-70d0-714d-97bc-dcd08c36e2fc" xlink:to="loc_srt_FitchBBBRatingMember_019caf13-70d0-7475-9b23-c3e23eef4271" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-7e85-bd66-c90222509b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019caf13-70d0-7bbd-be2e-180b4fccac46" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-7e85-bd66-c90222509b8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7e85-bd66-c90222509b8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-7e85-bd66-c90222509b8e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7e85-bd66-c90222509b8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7dcd-b09d-f63707cb1f8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-7e85-bd66-c90222509b8e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7dcd-b09d-f63707cb1f8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-70d0-70a3-894f-e4adfc523a32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7dcd-b09d-f63707cb1f8c" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-70d0-70a3-894f-e4adfc523a32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-70d0-7a7d-8651-aa1c102f393c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7dcd-b09d-f63707cb1f8c" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-70d0-7a7d-8651-aa1c102f393c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-70d0-71f8-b798-bb2f97b02ec2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-7dcd-b09d-f63707cb1f8c" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-70d0-71f8-b798-bb2f97b02ec2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-70d0-7010-ba22-600f9da3cf77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019caf13-70d0-7ef2-b3c5-406688d6b841" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-70d0-7010-ba22-600f9da3cf77" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/InvestmentSecuritiesScheduleofUnrealizedLossonInvestmentsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#InvestmentSecuritiesScheduleofUnrealizedLossonInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/InvestmentSecuritiesScheduleofUnrealizedLossonInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf13-70d0-739c-910e-8b604b917d22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf13-70d0-739c-910e-8b604b917d22" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-78b1-bdd3-86b958becce9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf13-70d0-739c-910e-8b604b917d22" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-78b1-bdd3-86b958becce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-78b1-bdd3-86b958becce9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-78b1-bdd3-86b958becce9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-78b1-bdd3-86b958becce9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d0-78b1-bdd3-86b958becce9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-70d0-7d82-a67c-66d796b4bc85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-70d0-7d82-a67c-66d796b4bc85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-70d0-74e7-b249-0011c614f2f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-70d0-74e7-b249-0011c614f2f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-70d0-7d01-8f39-2e79d5ff459d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-70d0-7d01-8f39-2e79d5ff459d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-70d0-78d2-9cbd-0b85280019a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-70d0-78d2-9cbd-0b85280019a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-70d0-7624-8e44-ee3784fb59d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-70d0-7624-8e44-ee3784fb59d9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-70d0-74a1-a59c-ad8cabf08429" xlink:href="ally-20260331.xsd#ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-70d0-74a1-a59c-ad8cabf08429" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-70d0-771c-b7a6-a730e3134d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-70d0-771c-b7a6-a730e3134d2d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-70d0-7bad-9d15-0718f2ea5441" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d0-797c-a4ec-7ca0387c21cd" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-70d0-7bad-9d15-0718f2ea5441" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019caf13-70d0-75fd-a1a9-e15f175d3b93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019caf13-70d0-75fd-a1a9-e15f175d3b93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019caf13-70d0-7254-af4a-58953a059b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019caf13-70d0-75fd-a1a9-e15f175d3b93" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019caf13-70d0-7254-af4a-58953a059b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019caf13-70d0-7932-99d5-b616e05e490a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019caf13-70d0-75fd-a1a9-e15f175d3b93" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019caf13-70d0-7932-99d5-b616e05e490a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesAvailableForSaleUnrealizedLossPositionLongAbstract_019caf13-70d0-7fee-aafb-9c8e95a8c662" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesAvailableForSaleUnrealizedLossPositionLongAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:to="loc_ally_DebtSecuritiesAvailableForSaleUnrealizedLossPositionLongAbstract_019caf13-70d0-7fee-aafb-9c8e95a8c662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019caf13-70d0-7892-b079-78f84b51f785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesAvailableForSaleUnrealizedLossPositionLongAbstract_019caf13-70d0-7fee-aafb-9c8e95a8c662" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019caf13-70d0-7892-b079-78f84b51f785" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019caf13-70d0-73c5-9a0b-7bcfa84070a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_DebtSecuritiesAvailableForSaleUnrealizedLossPositionLongAbstract_019caf13-70d0-7fee-aafb-9c8e95a8c662" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019caf13-70d0-73c5-9a0b-7bcfa84070a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-71ee-a721-0b0a30778281" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-71ee-a721-0b0a30778281" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-705d-8417-6a9691f64e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf13-70d0-7741-a296-469b04732dfe" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-705d-8417-6a9691f64e6b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofAccountsNotesLoansandFinancingReceivablesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofAccountsNotesLoansandFinancingReceivablesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofAccountsNotesLoansandFinancingReceivablesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7fbe-bc4c-5f6a0d45e48d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7fbe-bc4c-5f6a0d45e48d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7bca-9c10-86ce3f5aa3d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7fbe-bc4c-5f6a0d45e48d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7bca-9c10-86ce3f5aa3d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7bca-9c10-86ce3f5aa3d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7bca-9c10-86ce3f5aa3d6" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7bca-9c10-86ce3f5aa3d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7ec6-928a-83b93e61eecd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7bca-9c10-86ce3f5aa3d6" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7ec6-928a-83b93e61eecd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-72dd-bdb7-f1a863370d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7ec6-928a-83b93e61eecd" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-72dd-bdb7-f1a863370d0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7df2-9f1b-f3ecb744889c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7ec6-928a-83b93e61eecd" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7df2-9f1b-f3ecb744889c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-790b-b9a5-1190b1682744" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7fbe-bc4c-5f6a0d45e48d" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-790b-b9a5-1190b1682744" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-790b-b9a5-1190b1682744_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-790b-b9a5-1190b1682744" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-790b-b9a5-1190b1682744_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-78a4-8f05-21ab6142a2e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-790b-b9a5-1190b1682744" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-78a4-8f05-21ab6142a2e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7bb4-863f-f5d53c1e61cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-78a4-8f05-21ab6142a2e1" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7bb4-863f-f5d53c1e61cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7dc2-9aac-ba2d23e4442e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-78a4-8f05-21ab6142a2e1" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7dc2-9aac-ba2d23e4442e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-7221-932d-d36f67fefe24" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-78a4-8f05-21ab6142a2e1" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-7221-932d-d36f67fefe24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7ad9-b904-3d96e8f2ae98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7ad9-b904-3d96e8f2ae98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_HeldForInvestmentMortgageFinanceReceivablesInterestOnlyMortgageLoans_019caf13-70d0-7f90-b7e4-d89ad337af15" xlink:href="ally-20260331.xsd#ally_HeldForInvestmentMortgageFinanceReceivablesInterestOnlyMortgageLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:to="loc_ally_HeldForInvestmentMortgageFinanceReceivablesInterestOnlyMortgageLoans_019caf13-70d0-7f90-b7e4-d89ad337af15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019caf13-70d0-728c-a31a-4201749647b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:to="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019caf13-70d0-728c-a31a-4201749647b5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7849-806f-d4423ddb970a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7bc0-b4ec-1bbf61b7ddde" xlink:to="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7849-806f-d4423ddb970a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofAllowanceforCreditLossesonFinancingReceivablesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofAllowanceforCreditLossesonFinancingReceivablesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofAllowanceforCreditLossesonFinancingReceivablesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019caf13-70d0-723a-ba82-d66cedebe1e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019caf13-70d0-77f0-8eae-8068a140f539" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019caf13-70d0-723a-ba82-d66cedebe1e5" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019caf13-70d0-77f0-8eae-8068a140f539" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-794b-b637-83de265825b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019caf13-70d0-77f0-8eae-8068a140f539" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-794b-b637-83de265825b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-794b-b637-83de265825b9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-794b-b637-83de265825b9" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-794b-b637-83de265825b9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-761d-8a95-51d56a7df4b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-794b-b637-83de265825b9" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-761d-8a95-51d56a7df4b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7d18-9c86-275084cf497d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-761d-8a95-51d56a7df4b9" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7d18-9c86-275084cf497d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7764-a21f-99b816fdb2c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-761d-8a95-51d56a7df4b9" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7764-a21f-99b816fdb2c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7106-9a42-629a590cdccc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019caf13-70d0-77f0-8eae-8068a140f539" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7106-9a42-629a590cdccc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7106-9a42-629a590cdccc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7106-9a42-629a590cdccc" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7106-9a42-629a590cdccc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7bfa-b8b2-d12ff515821e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7106-9a42-629a590cdccc" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7bfa-b8b2-d12ff515821e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-759f-b51d-d729be019bf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7bfa-b8b2-d12ff515821e" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-759f-b51d-d729be019bf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7344-9a64-1835f63d7e19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7bfa-b8b2-d12ff515821e" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7344-9a64-1835f63d7e19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-7eb7-a1d5-8604f1a0c75a" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7bfa-b8b2-d12ff515821e" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-7eb7-a1d5-8604f1a0c75a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019caf13-70d0-723a-ba82-d66cedebe1e5" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-7b1e-8b16-33df49d31e3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-7b1e-8b16-33df49d31e3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019caf13-70d0-7aed-a02c-bed3b88cc8e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019caf13-70d0-7aed-a02c-bed3b88cc8e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_019caf13-70d0-73a8-868e-1528f765cb82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_019caf13-70d0-73a8-868e-1528f765cb82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_019caf13-70d0-76c9-a29f-745f076c2753" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_019caf13-70d0-76c9-a29f-745f076c2753" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019caf13-70d0-77dd-a57b-4d94521363c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019caf13-70d0-77dd-a57b-4d94521363c6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossOther_019caf13-70d0-7a52-b136-bbc0594afb31" xlink:href="ally-20260331.xsd#ally_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward_019caf13-70d0-724d-83a6-932fce2eb1fb" xlink:to="loc_ally_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossOther_019caf13-70d0-7a52-b136-bbc0594afb31" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019caf13-70d0-7acf-98d3-9de5ac11f077" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofSalesofFinancingReceivablesandLoansDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofSalesofFinancingReceivablesandLoansDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofSalesofFinancingReceivablesandLoansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-70b8-8df4-ba08da857aa6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7f33-acec-8579257bc189" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-70b8-8df4-ba08da857aa6" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7f33-acec-8579257bc189" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7fdf-9a81-a1b297411d46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7f33-acec-8579257bc189" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7fdf-9a81-a1b297411d46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7fdf-9a81-a1b297411d46_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7fdf-9a81-a1b297411d46" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7fdf-9a81-a1b297411d46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dd6-9104-78c9825fae14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7fdf-9a81-a1b297411d46" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dd6-9104-78c9825fae14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7f11-a99c-760fd8ed1e0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dd6-9104-78c9825fae14" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7f11-a99c-760fd8ed1e0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7c68-9ebd-ec20a24f615c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dd6-9104-78c9825fae14" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7c68-9ebd-ec20a24f615c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7f33-acec-8579257bc189" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7980-9c7d-a75d3a6028e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7ce2-a9ce-3c3bf4dd5dc2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7980-9c7d-a75d3a6028e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-75d0-8170-2af3569a4fa7" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7980-9c7d-a75d3a6028e2" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-75d0-8170-2af3569a4fa7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableSignificantSales_019caf13-70d0-7656-a5f8-4c006e0179f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableSignificantSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-70b8-8df4-ba08da857aa6" xlink:to="loc_us-gaap_FinancingReceivableSignificantSales_019caf13-70d0-7656-a5f8-4c006e0179f5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofPurchasesofFinancingReceivablesandLoansDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofPurchasesofFinancingReceivablesandLoansDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofPurchasesofFinancingReceivablesandLoansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7273-97e8-c38a5a7346f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-70c3-b01f-a74d48687900" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7273-97e8-c38a5a7346f7" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-70c3-b01f-a74d48687900" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c6d-b739-65f9f1f9c912" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-70c3-b01f-a74d48687900" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c6d-b739-65f9f1f9c912" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c6d-b739-65f9f1f9c912_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c6d-b739-65f9f1f9c912" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c6d-b739-65f9f1f9c912_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dc7-b048-c8ea77cce5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c6d-b739-65f9f1f9c912" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dc7-b048-c8ea77cce5fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7c1b-ab7f-57f7932f2928" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dc7-b048-c8ea77cce5fb" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7c1b-ab7f-57f7932f2928" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019d9e8c-2a5b-7672-a38b-8718ee767761" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7dc7-b048-c8ea77cce5fb" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019d9e8c-2a5b-7672-a38b-8718ee767761" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd3-ae19-3ef5d04a0deb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-70c3-b01f-a74d48687900" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd3-ae19-3ef5d04a0deb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7dd3-ae19-3ef5d04a0deb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd3-ae19-3ef5d04a0deb" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7dd3-ae19-3ef5d04a0deb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7c03-a523-5515a9111083" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd3-ae19-3ef5d04a0deb" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7c03-a523-5515a9111083" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-727c-a04b-294de3dd8cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7c03-a523-5515a9111083" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-727c-a04b-294de3dd8cc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-71d5-9e26-dbc1037628a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7c03-a523-5515a9111083" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-71d5-9e26-dbc1037628a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableSignificantPurchases_019caf13-70d0-7796-827e-6965ffa5fb81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableSignificantPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-7273-97e8-c38a5a7346f7" xlink:to="loc_us-gaap_FinancingReceivableSignificantPurchases_019caf13-70d0-7796-827e-6965ffa5fb81" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivablesNonaccrualStatusDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofFinancingReceivablesNonaccrualStatusDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivablesNonaccrualStatusDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-76ee-8615-051de684395c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7ffa-98b4-d84925f8105d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-76ee-8615-051de684395c" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7ffa-98b4-d84925f8105d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c47-b05f-843b1b7966a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7ffa-98b4-d84925f8105d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c47-b05f-843b1b7966a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c47-b05f-843b1b7966a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c47-b05f-843b1b7966a1" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c47-b05f-843b1b7966a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7be3-87a3-7c00b7b9d20c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7c47-b05f-843b1b7966a1" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7be3-87a3-7c00b7b9d20c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-78f1-af99-10f855b72e13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7be3-87a3-7c00b7b9d20c" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-78f1-af99-10f855b72e13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7b32-a7d5-d560a1e56bed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7be3-87a3-7c00b7b9d20c" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7b32-a7d5-d560a1e56bed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019caf13-70d0-7ffa-98b4-d84925f8105d" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7775-97d0-28c7a3492169" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7dd1-9dcf-6ed4a8f1c679" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7775-97d0-28c7a3492169" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7931-9296-5197d75d64ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7775-97d0-28c7a3492169" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7931-9296-5197d75d64ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-71d6-8782-c6bad8f6ae99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7775-97d0-28c7a3492169" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-71d6-8782-c6bad8f6ae99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-719b-958c-9ddbe616ddc5" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7775-97d0-28c7a3492169" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-719b-958c-9ddbe616ddc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_019caf13-70d0-7122-8256-dedf6aa0f55a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-76ee-8615-051de684395c" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_019caf13-70d0-7122-8256-dedf6aa0f55a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableNonaccrualNoAllowance_019caf13-70d0-7160-8f99-6bdf8d97bc67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableNonaccrualNoAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-76ee-8615-051de684395c" xlink:to="loc_us-gaap_FinancingReceivableNonaccrualNoAllowance_019caf13-70d0-7160-8f99-6bdf8d97bc67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableNonaccrualInterestIncome_019caf13-70d0-779e-a0bf-191d80511ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableNonaccrualInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019caf13-70d0-76ee-8615-051de684395c" xlink:to="loc_us-gaap_FinancingReceivableNonaccrualInterestIncome_019caf13-70d0-779e-a0bf-191d80511ecb" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsConsumerDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsConsumerDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsConsumerDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-718d-908d-aa7de26f1393" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-718d-908d-aa7de26f1393" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7e56-b0d0-918395dda98b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-718d-908d-aa7de26f1393" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7e56-b0d0-918395dda98b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7e56-b0d0-918395dda98b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7e56-b0d0-918395dda98b" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7e56-b0d0-918395dda98b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-78f5-83b4-d2a164f855e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7e56-b0d0-918395dda98b" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-78f5-83b4-d2a164f855e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-71fc-9efb-ab8bb144f6be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-78f5-83b4-d2a164f855e7" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-71fc-9efb-ab8bb144f6be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ConsumerPortfolioSegmentExcludesBasisAdjustmentForAutomotiveLoansMember_019caf13-70d0-7bdb-8e72-ce8dcbfb0522" xlink:href="ally-20260331.xsd#ally_ConsumerPortfolioSegmentExcludesBasisAdjustmentForAutomotiveLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-71fc-9efb-ab8bb144f6be" xlink:to="loc_ally_ConsumerPortfolioSegmentExcludesBasisAdjustmentForAutomotiveLoansMember_019caf13-70d0-7bdb-8e72-ce8dcbfb0522" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7773-9f47-0a7d9e5a6c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-718d-908d-aa7de26f1393" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7773-9f47-0a7d9e5a6c5e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7773-9f47-0a7d9e5a6c5e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7773-9f47-0a7d9e5a6c5e" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7773-9f47-0a7d9e5a6c5e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77d9-8eac-92005d1b3d13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7773-9f47-0a7d9e5a6c5e" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77d9-8eac-92005d1b3d13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AutomobileLoanExcludesBasisAdjustmentMember_019caf13-70d0-73d8-a5d1-0233140838ba" xlink:href="ally-20260331.xsd#ally_AutomobileLoanExcludesBasisAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77d9-8eac-92005d1b3d13" xlink:to="loc_ally_AutomobileLoanExcludesBasisAdjustmentMember_019caf13-70d0-73d8-a5d1-0233140838ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-799a-9225-6189f739acdd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77d9-8eac-92005d1b3d13" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-799a-9225-6189f739acdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7cf7-a864-c2d6a6130145" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77d9-8eac-92005d1b3d13" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7cf7-a864-c2d6a6130145" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-719b-9a9b-666849d858e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-718d-908d-aa7de26f1393" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-719b-9a9b-666849d858e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-719b-9a9b-666849d858e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-719b-9a9b-666849d858e1" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-719b-9a9b-666849d858e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-719b-9a9b-666849d858e1" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d0-7dd3-8d72-8e0def5a9c63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d0-7dd3-8d72-8e0def5a9c63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d0-71e0-9763-71f10fa133c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d0-71e0-9763-71f10fa133c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d0-736b-b550-1e762fee0627" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d0-736b-b550-1e762fee0627" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d0-7386-bc21-532f1fae471d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-7cdf-80cb-eb9ff0b529e9" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d0-7386-bc21-532f1fae471d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019caf13-70d0-7ff0-854b-83acf6758cc5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019caf13-70d0-7ff0-854b-83acf6758cc5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019caf13-70d0-7d16-aff3-50b0bfe394e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019caf13-70d0-7d16-aff3-50b0bfe394e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019caf13-70d0-796a-800c-c1ecbdbeddd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019caf13-70d0-796a-800c-c1ecbdbeddd9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019caf13-70d0-79c2-b54d-66dabf37b0e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019caf13-70d0-79c2-b54d-66dabf37b0e0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019caf13-70d0-7dcb-b59d-5201b9b0073e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019caf13-70d0-7dcb-b59d-5201b9b0073e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019caf13-70d0-740c-9fd9-e8fd288f0833" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019caf13-70d0-740c-9fd9-e8fd288f0833" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019caf13-70d0-7472-a444-03da615a13ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019caf13-70d0-7472-a444-03da615a13ac" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019caf13-70d0-71ff-b168-549fdff48c14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019caf13-70d0-71ff-b168-549fdff48c14" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7852-a1c6-e5b4e17c8450" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7852-a1c6-e5b4e17c8450" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_HedgedAssetFairValueHedgePortfolioLayerMethodLiabilityHeldAgainstAmortizedCostOfHedgedAsset_019d9e97-28d9-77e5-8459-c4ce840cddbd" xlink:href="ally-20260331.xsd#ally_HedgedAssetFairValueHedgePortfolioLayerMethodLiabilityHeldAgainstAmortizedCostOfHedgedAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_ally_HedgedAssetFairValueHedgePortfolioLayerMethodLiabilityHeldAgainstAmortizedCostOfHedgedAsset_019d9e97-28d9-77e5-8459-c4ce840cddbd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgePortfolioLayerMethodCumulativeIncreaseDecreaseExcludedFromAmortizedCost_019d9e99-8948-7bc1-a1d3-ac600d579ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgePortfolioLayerMethodCumulativeIncreaseDecreaseExcludedFromAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-735d-87d5-3746b52afd30" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgePortfolioLayerMethodCumulativeIncreaseDecreaseExcludedFromAmortizedCost_019d9e99-8948-7bc1-a1d3-ac600d579ad4" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsCommercialDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsCommercialDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableCreditQualityIndicatorsCommercialDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-7000-aa31-81e62d2e36b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-7000-aa31-81e62d2e36b5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-73e1-b282-7f785cc783d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-7000-aa31-81e62d2e36b5" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-73e1-b282-7f785cc783d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73e1-b282-7f785cc783d3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-73e1-b282-7f785cc783d3" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73e1-b282-7f785cc783d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-743b-9db6-b4b8132504d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-73e1-b282-7f785cc783d3" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-743b-9db6-b4b8132504d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7477-916e-6fee34854762" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-743b-9db6-b4b8132504d9" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7477-916e-6fee34854762" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7d47-941f-03ca986590ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-7000-aa31-81e62d2e36b5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7d47-941f-03ca986590ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7d47-941f-03ca986590ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7d47-941f-03ca986590ad" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7d47-941f-03ca986590ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77c6-b147-22a58d6c3847" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7d47-941f-03ca986590ad" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77c6-b147-22a58d6c3847" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7a09-a8c8-aa6cfe34b41a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77c6-b147-22a58d6c3847" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-7a09-a8c8-aa6cfe34b41a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-756c-8695-33d95ffe1b43" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77c6-b147-22a58d6c3847" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-756c-8695-33d95ffe1b43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7ebb-b65f-535db525e94c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-77c6-b147-22a58d6c3847" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7ebb-b65f-535db525e94c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d0-79f6-a8c5-c65db670cc23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-7000-aa31-81e62d2e36b5" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d0-79f6-a8c5-c65db670cc23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-79f6-a8c5-c65db670cc23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d0-79f6-a8c5-c65db670cc23" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-79f6-a8c5-c65db670cc23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d0-79f6-a8c5-c65db670cc23" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassMember_019caf13-70d0-7ab1-b364-df1dc5b5fb1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:to="loc_us-gaap_PassMember_019caf13-70d0-7ab1-b364-df1dc5b5fb1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SpecialMentionMember_019caf13-70d0-78e2-8c3d-098a880366c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SpecialMentionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:to="loc_us-gaap_SpecialMentionMember_019caf13-70d0-78e2-8c3d-098a880366c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubstandardMember_019caf13-70d0-7976-bf20-36933578427f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubstandardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:to="loc_us-gaap_SubstandardMember_019caf13-70d0-7976-bf20-36933578427f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DoubtfulMember_019caf13-70d0-7bbf-89f3-2639f485fdb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DoubtfulMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d0-78ba-83b3-82309892cf2d" xlink:to="loc_us-gaap_DoubtfulMember_019caf13-70d0-7bbf-89f3-2639f485fdb2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019caf13-70d0-7d5c-ac28-2b8d0f932d7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019caf13-70d0-7d5c-ac28-2b8d0f932d7e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019caf13-70d0-7ab7-bdc6-2e30e65743b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019caf13-70d0-7ab7-bdc6-2e30e65743b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019caf13-70d0-700c-ad43-c172ec2f8042" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019caf13-70d0-700c-ad43-c172ec2f8042" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019caf13-70d0-7b7b-9c33-ee1a35db6342" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019caf13-70d0-7b7b-9c33-ee1a35db6342" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019caf13-70d0-7999-86a1-12e02beb02b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019caf13-70d0-7999-86a1-12e02beb02b6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019caf13-70d0-7081-8072-8b3f5dc4d895" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019caf13-70d0-7081-8072-8b3f5dc4d895" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019caf13-70d0-7df4-8bca-15ed3e33913d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019caf13-70d0-7df4-8bca-15ed3e33913d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019caf13-70d0-7868-9c83-ed89f4a89e14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019caf13-70d0-7868-9c83-ed89f4a89e14" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-754b-9514-71b86b20973a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-737d-9c1e-6839c20f3b85" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-754b-9514-71b86b20973a" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofPastDueFinancingReceivablesandLoansCommercialDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofPastDueFinancingReceivablesandLoansCommercialDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofPastDueFinancingReceivablesandLoansCommercialDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019caf13-70d0-7adf-aad4-62324637e2bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019caf13-70d0-7ce1-8546-b5182ea00b33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019caf13-70d0-7adf-aad4-62324637e2bf" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019caf13-70d0-7ce1-8546-b5182ea00b33" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-75d0-8d06-c1c850a1b368" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019caf13-70d0-7ce1-8546-b5182ea00b33" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-75d0-8d06-c1c850a1b368" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-75d0-8d06-c1c850a1b368_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-75d0-8d06-c1c850a1b368" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-75d0-8d06-c1c850a1b368_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c2b-8e21-27347910e332" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-75d0-8d06-c1c850a1b368" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c2b-8e21-27347910e332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7597-8ea0-eba5d6eaf875" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7c2b-8e21-27347910e332" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7597-8ea0-eba5d6eaf875" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-734a-810f-2930deb98c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019caf13-70d0-7ce1-8546-b5182ea00b33" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-734a-810f-2930deb98c9b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-734a-810f-2930deb98c9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-734a-810f-2930deb98c9b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-734a-810f-2930deb98c9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7502-aa0f-92865e8ced6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-734a-810f-2930deb98c9b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7502-aa0f-92865e8ced6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-719b-b83d-9f6b7ee65e3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7502-aa0f-92865e8ced6c" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-719b-b83d-9f6b7ee65e3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-7d6c-b4d7-c847aa75408a" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7502-aa0f-92865e8ced6c" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-7d6c-b4d7-c847aa75408a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-77c4-b06d-4ca93ece2ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7502-aa0f-92865e8ced6c" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-77c4-b06d-4ca93ece2ecb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-74ba-88d0-38848574eaa3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019caf13-70d0-7ce1-8546-b5182ea00b33" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-74ba-88d0-38848574eaa3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-74ba-88d0-38848574eaa3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-74ba-88d0-38848574eaa3" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-74ba-88d0-38848574eaa3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-72ae-9fef-aa8607776897" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d0-74ba-88d0-38848574eaa3" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-72ae-9fef-aa8607776897" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetPastDueMember_019caf13-70d0-7c3d-8f98-540f522c271b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-72ae-9fef-aa8607776897" xlink:to="loc_us-gaap_FinancialAssetPastDueMember_019caf13-70d0-7c3d-8f98-540f522c271b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d0-75eb-ab29-4a563988b2a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialAssetPastDueMember_019caf13-70d0-7c3d-8f98-540f522c271b" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d0-75eb-ab29-4a563988b2a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d0-783d-9042-3182d033c78f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialAssetPastDueMember_019caf13-70d0-7c3d-8f98-540f522c271b" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d0-783d-9042-3182d033c78f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d0-735c-8df3-1e76f6092f4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialAssetPastDueMember_019caf13-70d0-7c3d-8f98-540f522c271b" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d0-735c-8df3-1e76f6092f4b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d0-7b1f-b00c-9f091a327b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d0-72ae-9fef-aa8607776897" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d0-7b1f-b00c-9f091a327b7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7cbf-bb57-c8f1a2ae143a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019caf13-70d0-7adf-aad4-62324637e2bf" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019caf13-70d0-7cbf-bb57-c8f1a2ae143a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableGrossChargeOffsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofFinancingReceivableGrossChargeOffsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofFinancingReceivableGrossChargeOffsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-79bc-81a9-560146c3afe5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-79bc-81a9-560146c3afe5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7eb9-9ae9-270a36fb75ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-79bc-81a9-560146c3afe5" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7eb9-9ae9-270a36fb75ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7eb9-9ae9-270a36fb75ea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7eb9-9ae9-270a36fb75ea" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-7eb9-9ae9-270a36fb75ea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73f7-af19-a83750e0ce25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d0-7eb9-9ae9-270a36fb75ea" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73f7-af19-a83750e0ce25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7774-8f41-4b383b953130" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73f7-af19-a83750e0ce25" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d0-7774-8f41-4b383b953130" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7645-93e0-830279eae62f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d0-73f7-af19-a83750e0ce25" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d0-7645-93e0-830279eae62f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7e26-ac87-87c4baa38fb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019caf13-70d0-79bc-81a9-560146c3afe5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7e26-ac87-87c4baa38fb1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7e26-ac87-87c4baa38fb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7e26-ac87-87c4baa38fb1" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-7e26-ac87-87c4baa38fb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-759a-abc0-5d90c7f98ee0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d0-7e26-ac87-87c4baa38fb1" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-759a-abc0-5d90c7f98ee0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-75c2-aed2-c3565751386b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-759a-abc0-5d90c7f98ee0" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d0-75c2-aed2-c3565751386b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7140-bf70-e559528498fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-759a-abc0-5d90c7f98ee0" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d0-7140-bf70-e559528498fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d0-7575-9b65-3a8a2ccd67c4" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d0-759a-abc0-5d90c7f98ee0" xlink:to="loc_ally_OtherLoansMember_019caf13-70d0-7575-9b65-3a8a2ccd67c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019caf13-70d0-745e-a30e-e4765feb03c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019caf13-70d0-745e-a30e-e4765feb03c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019caf13-70d0-791a-8aa3-2d32d6c2f3fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019caf13-70d0-791a-8aa3-2d32d6c2f3fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7aa9-a7a2-cd8c4dbad5bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7aa9-a7a2-cd8c4dbad5bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7886-b64f-15d818b79ced" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7886-b64f-15d818b79ced" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-78fd-8645-cc77431cff61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-78fd-8645-cc77431cff61" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7066-8d8a-c6e49fc3c581" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019caf13-70d0-7066-8d8a-c6e49fc3c581" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019caf13-70d1-7142-a031-eee270465e86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019caf13-70d1-7142-a031-eee270465e86" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019caf13-70d1-7283-b6f0-9742af345b6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019caf13-70d1-7283-b6f0-9742af345b6d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019caf13-70d1-72a7-a897-0406ff6400db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019caf13-70d1-72a7-a897-0406ff6400db" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestTransferToHeldForSaleAllowanceForCreditLossExpenseReversal_019caf13-70d1-7ab4-a0bf-f283c2f3e31b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestTransferToHeldForSaleAllowanceForCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019caf13-70d0-72b5-ac87-a0f9833d839e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestTransferToHeldForSaleAllowanceForCreditLossExpenseReversal_019caf13-70d1-7ab4-a0bf-f283c2f3e31b" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofLoanModificationsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FinanceReceivablesandLoansNetScheduleofLoanModificationsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FinanceReceivablesandLoansNetScheduleofLoanModificationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModificationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-772c-ba15-6e257f87d0fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-772c-ba15-6e257f87d0fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-772c-ba15-6e257f87d0fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-772c-ba15-6e257f87d0fe" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-772c-ba15-6e257f87d0fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-72d4-918f-406169081345" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-772c-ba15-6e257f87d0fe" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-72d4-918f-406169081345" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-71ff-b9bc-c580e211e766" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-72d4-918f-406169081345" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-71ff-b9bc-c580e211e766" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-7145-afbb-c1692124560a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-72d4-918f-406169081345" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-7145-afbb-c1692124560a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7527-9c8e-f0484fdf411b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7527-9c8e-f0484fdf411b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7527-9c8e-f0484fdf411b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7527-9c8e-f0484fdf411b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7527-9c8e-f0484fdf411b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7527-9c8e-f0484fdf411b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-76fc-bb94-89e7955dd8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-76fc-bb94-89e7955dd8bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-70d1-70b7-891c-33e1c2fd97e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-70d1-70b7-891c-33e1c2fd97e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d1-7907-b435-f8501dc7e52a" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:to="loc_ally_OtherLoansMember_019caf13-70d1-7907-b435-f8501dc7e52a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_019d9ee4-a859-7c26-a423-eeca360baa4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-772a-8488-d3056c1571e6" xlink:to="loc_us-gaap_CommercialRealEstateMember_019d9ee4-a859-7c26-a423-eeca360baa4c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_019caf13-70d1-733a-bf01-2dc6452fa6c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_019caf13-70d1-733a-bf01-2dc6452fa6c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-733a-bf01-2dc6452fa6c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019caf13-70d1-733a-bf01-2dc6452fa6c2" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-733a-bf01-2dc6452fa6c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019caf13-70d1-733a-bf01-2dc6452fa6c2" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentDeferralMember_019caf13-70d1-785d-a4dd-c5064a6d6cad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentDeferralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:to="loc_us-gaap_PaymentDeferralMember_019caf13-70d1-785d-a4dd-c5064a6d6cad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtendedMaturityMember_019caf13-70d1-7dbd-9698-2e9e237bed50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ExtendedMaturityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:to="loc_us-gaap_ExtendedMaturityMember_019caf13-70d1-7dbd-9698-2e9e237bed50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrincipalForgivenessMember_019caf13-70d1-7c26-ae5b-4171df4c331a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrincipalForgivenessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:to="loc_us-gaap_PrincipalForgivenessMember_019caf13-70d1-7c26-ae5b-4171df4c331a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualInterestRateReductionMember_019caf13-70d1-780c-a919-6feb6c62c557" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractualInterestRateReductionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:to="loc_us-gaap_ContractualInterestRateReductionMember_019caf13-70d1-780c-a919-6feb6c62c557" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtendedMaturityAndInterestRateReductionMember_019caf13-70d1-7c15-b692-8f96208e912e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ExtendedMaturityAndInterestRateReductionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019caf13-70d1-7022-8732-a7f8b07979e4" xlink:to="loc_us-gaap_ExtendedMaturityAndInterestRateReductionMember_019caf13-70d1-7c15-b692-8f96208e912e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d1-7039-a417-e1860dca68ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d1-7039-a417-e1860dca68ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-7039-a417-e1860dca68ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d1-7039-a417-e1860dca68ba" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-7039-a417-e1860dca68ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019caf13-70d1-7039-a417-e1860dca68ba" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d1-72ab-8456-1cdbfb4daed0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019caf13-70d1-72ab-8456-1cdbfb4daed0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d1-7ef1-ab89-b2edfa5f54b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019caf13-70d1-7ef1-ab89-b2edfa5f54b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d1-74a9-894c-477a4adea930" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_019caf13-70d1-74a9-894c-477a4adea930" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d1-7a7f-9981-a5640ff236b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019caf13-70d1-770e-b962-13225edb2571" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019caf13-70d1-7a7f-9981-a5640ff236b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d1-7f89-b8b0-5c0e15776444" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019caf13-70d1-7f74-97dc-d149c97af800" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d1-7f89-b8b0-5c0e15776444" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-7f89-b8b0-5c0e15776444_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d1-7f89-b8b0-5c0e15776444" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-7f89-b8b0-5c0e15776444_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019caf13-70d1-7f89-b8b0-5c0e15776444" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassMember_019caf13-70d1-7121-a88a-de697d6c147d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:to="loc_us-gaap_PassMember_019caf13-70d1-7121-a88a-de697d6c147d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SpecialMentionMember_019caf13-70d1-7900-bf63-93f9fa0b7c15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SpecialMentionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:to="loc_us-gaap_SpecialMentionMember_019caf13-70d1-7900-bf63-93f9fa0b7c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubstandardMember_019caf13-70d1-79d8-bcf9-f6fd2cc78fad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubstandardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:to="loc_us-gaap_SubstandardMember_019caf13-70d1-79d8-bcf9-f6fd2cc78fad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DoubtfulMember_019caf13-70d1-7018-8f1a-30ea4d9110ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DoubtfulMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019caf13-70d1-76cd-accc-899f7ac4e258" xlink:to="loc_us-gaap_DoubtfulMember_019caf13-70d1-7018-8f1a-30ea4d9110ac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableTrialModificationsTerm_019caf13-70d1-7bea-a6c0-471ff8ef4242" xlink:href="ally-20260331.xsd#ally_FinancingReceivableTrialModificationsTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableTrialModificationsTerm_019caf13-70d1-7bea-a6c0-471ff8ef4242" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableTrialModificationsAmount_019caf13-70d1-76ba-bece-1721fc7386b7" xlink:href="ally-20260331.xsd#ally_FinancingReceivableTrialModificationsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableTrialModificationsAmount_019caf13-70d1-76ba-bece-1721fc7386b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod_019caf13-70d1-7a70-9cba-4bb83548a6a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod_019caf13-70d1-7a70-9cba-4bb83548a6a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent_019caf13-70d1-7629-84fe-391563b00e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent_019caf13-70d1-7629-84fe-391563b00e6b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification_019caf13-70d1-7b18-bb17-db887a8fc9ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification_019caf13-70d1-7b18-bb17-db887a8fc9ce" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableModifiedPrincipalForgivenessAmount_019caf13-70d1-7bfd-b238-601951c48436" xlink:href="ally-20260331.xsd#ally_FinancingReceivableModifiedPrincipalForgivenessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableModifiedPrincipalForgivenessAmount_019caf13-70d1-7bfd-b238-601951c48436" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableModifiedWeightedAverageInterestRateInitialRate_019caf13-70d1-7f9e-bd17-b835ffbc8d27" xlink:href="ally-20260331.xsd#ally_FinancingReceivableModifiedWeightedAverageInterestRateInitialRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableModifiedWeightedAverageInterestRateInitialRate_019caf13-70d1-7f9e-bd17-b835ffbc8d27" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableModifiedWeightedAverageInterestRateRevisedRate_019caf13-70d1-7fd3-ad66-cea9c686d130" xlink:href="ally-20260331.xsd#ally_FinancingReceivableModifiedWeightedAverageInterestRateRevisedRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableModifiedWeightedAverageInterestRateRevisedRate_019caf13-70d1-7fd3-ad66-cea9c686d130" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableModifiedWeightedAverageTermBeforeModification_019caf13-70d1-79b9-8b84-7d405229c9ba" xlink:href="ally-20260331.xsd#ally_FinancingReceivableModifiedWeightedAverageTermBeforeModification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableModifiedWeightedAverageTermBeforeModification_019caf13-70d1-79b9-8b84-7d405229c9ba" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableModifiedWeightedAverageTermAfterModification_019caf13-70d1-789d-ae99-61cda90c6bb8" xlink:href="ally-20260331.xsd#ally_FinancingReceivableModifiedWeightedAverageTermAfterModification"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableModifiedWeightedAverageTermAfterModification_019caf13-70d1-789d-ae99-61cda90c6bb8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefaultNumberOfContracts_019caf13-70d1-7c87-9ce0-80f2dbe2fc90" xlink:href="ally-20260331.xsd#ally_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefaultNumberOfContracts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_ally_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefaultNumberOfContracts_019caf13-70d1-7c87-9ce0-80f2dbe2fc90" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefault_019caf13-70d1-73e8-abd0-ddfe2bfa0169" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefault"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019caf13-70d1-71bd-bb7b-ff6e39a577d9" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedSubsequentDefault_019caf13-70d1-73e8-abd0-ddfe2bfa0169" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/LeasingAllyastheLesseeDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#LeasingAllyastheLesseeDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/LeasingAllyastheLesseeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019caf13-70d1-763a-90a2-ee6c1a981cad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019caf13-70d1-763a-90a2-ee6c1a981cad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019caf13-70d1-788e-833a-316cc61e6d6f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019caf13-70d1-763a-90a2-ee6c1a981cad" xlink:to="loc_srt_RangeAxis_019caf13-70d1-788e-833a-316cc61e6d6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019caf13-70d1-788e-833a-316cc61e6d6f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019caf13-70d1-788e-833a-316cc61e6d6f" xlink:to="loc_srt_RangeMember_019caf13-70d1-788e-833a-316cc61e6d6f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019caf13-70d1-7066-b689-43c94c320bf0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019caf13-70d1-788e-833a-316cc61e6d6f" xlink:to="loc_srt_RangeMember_019caf13-70d1-7066-b689-43c94c320bf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019caf13-70d1-79f7-a738-993a19dbdd0c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019caf13-70d1-7066-b689-43c94c320bf0" xlink:to="loc_srt_MinimumMember_019caf13-70d1-79f7-a738-993a19dbdd0c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019caf13-70d1-72fc-bda3-4427e430e2cb" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019caf13-70d1-7066-b689-43c94c320bf0" xlink:to="loc_srt_MaximumMember_019caf13-70d1-72fc-bda3-4427e430e2cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_019caf13-70d1-7aa0-bd38-40c7f7cd11d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_019caf13-70d1-7aa0-bd38-40c7f7cd11d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LesseeOperatingLeaseNoncancellableLeaseTerm_019caf13-70d1-7b3a-bfc9-598a920239b5" xlink:href="ally-20260331.xsd#ally_LesseeOperatingLeaseNoncancellableLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_ally_LesseeOperatingLeaseNoncancellableLeaseTerm_019caf13-70d1-7b3a-bfc9-598a920239b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LesseeOperatingLeaseLeaseExtensionMaximum_019caf13-70d1-77b6-bee3-ec854ab08e36" xlink:href="ally-20260331.xsd#ally_LesseeOperatingLeaseLeaseExtensionMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_ally_LesseeOperatingLeaseLeaseExtensionMaximum_019caf13-70d1-77b6-bee3-ec854ab08e36" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilities_019caf13-70d1-7962-a9ba-1c0e7fbfa4bf" xlink:href="ally-20260331.xsd#ally_CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_ally_CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilities_019caf13-70d1-7962-a9ba-1c0e7fbfa4bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019caf13-70d1-7fa8-96ae-57b6ee924da2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019caf13-70d1-7fa8-96ae-57b6ee924da2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_019caf13-70d1-7c7d-8ccf-d7077b10541f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_019caf13-70d1-7c7d-8ccf-d7077b10541f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_019caf13-70d1-7af7-bfd0-355dc14b0926" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019caf13-70d1-76a5-91d0-ef68bf5a5593" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_019caf13-70d1-7af7-bfd0-355dc14b0926" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/LeasingScheduleofAllyastheLessorDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#LeasingScheduleofAllyastheLessorDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/LeasingScheduleofAllyastheLessorDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_019caf13-70d1-7d69-8f86-f255dbc72f57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_019caf13-70d1-7d69-8f86-f255dbc72f57" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019caf13-70d1-79d5-ab94-8db087b64b03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_019caf13-70d1-7d69-8f86-f255dbc72f57" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019caf13-70d1-79d5-ab94-8db087b64b03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019caf13-70d1-79d5-ab94-8db087b64b03_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019caf13-70d1-79d5-ab94-8db087b64b03" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019caf13-70d1-79d5-ab94-8db087b64b03_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019caf13-70d1-79bd-bc84-54b648a88d06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019caf13-70d1-79d5-ab94-8db087b64b03" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019caf13-70d1-79bd-bc84-54b648a88d06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VehiclesMember_019caf13-70d1-7e08-8a6e-974a10b6e59e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VehiclesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019caf13-70d1-79bd-bc84-54b648a88d06" xlink:to="loc_us-gaap_VehiclesMember_019caf13-70d1-7e08-8a6e-974a10b6e59e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019caf13-70d1-79f7-9326-76de7ec83221" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_019caf13-70d1-7d69-8f86-f255dbc72f57" xlink:to="loc_srt_RangeAxis_019caf13-70d1-79f7-9326-76de7ec83221" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019caf13-70d1-79f7-9326-76de7ec83221_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019caf13-70d1-79f7-9326-76de7ec83221" xlink:to="loc_srt_RangeMember_019caf13-70d1-79f7-9326-76de7ec83221_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019caf13-70d1-7f88-80db-8f67cfb1319d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019caf13-70d1-79f7-9326-76de7ec83221" xlink:to="loc_srt_RangeMember_019caf13-70d1-7f88-80db-8f67cfb1319d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019caf13-70d1-715c-9693-88cb4d2ffa8a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019caf13-70d1-7f88-80db-8f67cfb1319d" xlink:to="loc_srt_MinimumMember_019caf13-70d1-715c-9693-88cb4d2ffa8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019caf13-70d1-7987-90d7-94a774fa3537" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019caf13-70d1-7f88-80db-8f67cfb1319d" xlink:to="loc_srt_MaximumMember_019caf13-70d1-7987-90d7-94a774fa3537" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ResidualValueOfLeasedAssetAxis_019caf13-70d1-72af-b22b-9cc44efdac0f" xlink:href="ally-20260331.xsd#ally_ResidualValueOfLeasedAssetAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_019caf13-70d1-7d69-8f86-f255dbc72f57" xlink:to="loc_ally_ResidualValueOfLeasedAssetAxis_019caf13-70d1-72af-b22b-9cc44efdac0f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ResidualValueOfLeasedAssetDomain_019caf13-70d1-72af-b22b-9cc44efdac0f_default" xlink:href="ally-20260331.xsd#ally_ResidualValueOfLeasedAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ally_ResidualValueOfLeasedAssetAxis_019caf13-70d1-72af-b22b-9cc44efdac0f" xlink:to="loc_ally_ResidualValueOfLeasedAssetDomain_019caf13-70d1-72af-b22b-9cc44efdac0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ResidualValueOfLeasedAssetDomain_019caf13-70d1-7a5c-aae2-5c1bff9f9ffd" xlink:href="ally-20260331.xsd#ally_ResidualValueOfLeasedAssetDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ally_ResidualValueOfLeasedAssetAxis_019caf13-70d1-72af-b22b-9cc44efdac0f" xlink:to="loc_ally_ResidualValueOfLeasedAssetDomain_019caf13-70d1-7a5c-aae2-5c1bff9f9ffd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_A50OfVehicleResidualValueMember_019caf13-70d1-7fa7-b0d8-9ed4dc028648" xlink:href="ally-20260331.xsd#ally_A50OfVehicleResidualValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_ResidualValueOfLeasedAssetDomain_019caf13-70d1-7a5c-aae2-5c1bff9f9ffd" xlink:to="loc_ally_A50OfVehicleResidualValueMember_019caf13-70d1-7fa7-b0d8-9ed4dc028648" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorOperatingLeaseTermOfContract_019caf13-70d1-7d60-a6e9-9d4f7add0619" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LessorOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_LessorOperatingLeaseTermOfContract_019caf13-70d1-7d60-a6e9-9d4f7add0619" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseResidualValueOfLeasedAsset_019caf13-70d1-78cd-a6e7-d1a62e316d70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseResidualValueOfLeasedAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_OperatingLeaseResidualValueOfLeasedAsset_019caf13-70d1-78cd-a6e7-d1a62e316d70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ResidualValueGuarantee_019caf13-70d1-708d-9bae-9e72bdcc3737" xlink:href="ally-20260331.xsd#ally_ResidualValueGuarantee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_ally_ResidualValueGuarantee_019caf13-70d1-708d-9bae-9e72bdcc3737" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseGross_019caf13-70d1-772f-8292-5fb57aa1d104" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseGross_019caf13-70d1-772f-8292-5fb57aa1d104" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAccumulatedDepreciation_019caf13-70d1-72ae-acd6-cbe2a6f90375" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAccumulatedDepreciation_019caf13-70d1-72ae-acd6-cbe2a6f90375" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNet_019caf13-70d1-78d9-acc8-4fc0d91fafbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_019caf13-70d1-71f8-84a9-39c60adb6e00" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNet_019caf13-70d1-78d9-acc8-4fc0d91fafbc" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofVariableInterestEntitiesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#SecuritizationsandVariableInterestEntitiesScheduleofVariableInterestEntitiesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofVariableInterestEntitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-71be-9dd4-377a3778cb2e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-71be-9dd4-377a3778cb2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-71be-9dd4-377a3778cb2e_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-71be-9dd4-377a3778cb2e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-71be-9dd4-377a3778cb2e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-7866-b268-f32c13ac4164" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-71be-9dd4-377a3778cb2e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-7866-b268-f32c13ac4164" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_VariableInterestEntityMember_019caf13-70d1-76fb-aac4-f3c61e8e950d" xlink:href="ally-20260331.xsd#ally_VariableInterestEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-7866-b268-f32c13ac4164" xlink:to="loc_ally_VariableInterestEntityMember_019caf13-70d1-76fb-aac4-f3c61e8e950d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019caf13-70d1-7844-ad51-de5302455e9d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_VariableInterestEntityMember_019caf13-70d1-76fb-aac4-f3c61e8e950d" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019caf13-70d1-7844-ad51-de5302455e9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7e28-95d4-754d5fec2112" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_VariableInterestEntityMember_019caf13-70d1-76fb-aac4-f3c61e8e950d" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7e28-95d4-754d5fec2112" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-74a5-a106-90dca91acade" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-74a5-a106-90dca91acade" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-74a5-a106-90dca91acade_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-74a5-a106-90dca91acade" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-74a5-a106-90dca91acade_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7651-b3c5-6c5edbc669e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-74a5-a106-90dca91acade" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7651-b3c5-6c5edbc669e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7807-9745-ccdffebd1161" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7651-b3c5-6c5edbc669e8" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7807-9745-ccdffebd1161" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-78ad-8585-6b9e9616abf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7651-b3c5-6c5edbc669e8" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-78ad-8585-6b9e9616abf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-78cc-b8d4-d81bfaa3b298" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-78cc-b8d4-d81bfaa3b298" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-78cc-b8d4-d81bfaa3b298_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-78cc-b8d4-d81bfaa3b298" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-78cc-b8d4-d81bfaa3b298_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7826-961a-3ee66a899735" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-78cc-b8d4-d81bfaa3b298" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7826-961a-3ee66a899735" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-7cb5-b44a-33355959c17b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7826-961a-3ee66a899735" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-7cb5-b44a-33355959c17b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d1-7f26-90dd-e2f14735c4f2" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7826-961a-3ee66a899735" xlink:to="loc_ally_OtherLoansMember_019caf13-70d1-7f26-90dd-e2f14735c4f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusAxis_019caf13-70d1-78ba-abf0-3689b703fca5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RecourseStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019caf13-70d1-772f-a34b-dc9b9c658373" xlink:to="loc_us-gaap_RecourseStatusAxis_019caf13-70d1-78ba-abf0-3689b703fca5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusDomain_019caf13-70d1-78ba-abf0-3689b703fca5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RecourseStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RecourseStatusAxis_019caf13-70d1-78ba-abf0-3689b703fca5" xlink:to="loc_us-gaap_RecourseStatusDomain_019caf13-70d1-78ba-abf0-3689b703fca5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RecourseStatusDomain_019caf13-70d1-7132-9144-8962ecc58069" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RecourseStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RecourseStatusAxis_019caf13-70d1-78ba-abf0-3689b703fca5" xlink:to="loc_us-gaap_RecourseStatusDomain_019caf13-70d1-7132-9144-8962ecc58069" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecourseMember_019caf13-70d1-7f97-ad95-038c68f6aa5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonrecourseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RecourseStatusDomain_019caf13-70d1-7132-9144-8962ecc58069" xlink:to="loc_us-gaap_NonrecourseMember_019caf13-70d1-7f97-ad95-038c68f6aa5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019caf13-70d1-7f6e-9544-ec23a12fed21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_Assets_019caf13-70d1-7f6e-9544-ec23a12fed21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019caf13-70d1-75be-8e64-fa1387f5710b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_Liabilities_019caf13-70d1-75be-8e64-fa1387f5710b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContinuingInvolvementWithTransferredFinancialAssetsPrincipalAmountOutstanding_019caf13-70d1-7ecb-b9b7-1116d548c598" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContinuingInvolvementWithTransferredFinancialAssetsPrincipalAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_ContinuingInvolvementWithTransferredFinancialAssetsPrincipalAmountOutstanding_019caf13-70d1-7ecb-b9b7-1116d548c598" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount_019caf13-70d1-7c0f-a2db-8f4a534edf0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount_019caf13-70d1-7c0f-a2db-8f4a534edf0d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsHeldInTrust_019caf13-70d1-78e0-b2ef-9c2cd2b17a14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsHeldInTrust"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_AssetsHeldInTrust_019caf13-70d1-78e0-b2ef-9c2cd2b17a14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019caf13-70d1-7a1f-a7a7-366346a6abee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_LongTermDebt_019caf13-70d1-7a1f-a7a7-366346a6abee" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-70d1-74aa-9fdd-9ae638d98c09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-70d1-74aa-9fdd-9ae638d98c09" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019caf13-70d1-71b1-a336-9126184cb93e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_OtherAssets_019caf13-70d1-71b1-a336-9126184cb93e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019caf13-70d1-716b-83e5-8844cf328b03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019caf13-70d1-713e-801d-2783b43d3f43" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019caf13-70d1-716b-83e5-8844cf328b03" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofCashFlowswithNonconsolidatedSpecialPurposeEntitiesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#SecuritizationsandVariableInterestEntitiesScheduleofCashFlowswithNonconsolidatedSpecialPurposeEntitiesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofCashFlowswithNonconsolidatedSpecialPurposeEntitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable_019caf13-70d1-7314-afec-2218bd532bae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:to="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable_019caf13-70d1-7314-afec-2218bd532bae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-7039-a33b-ef913f0ab678" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable_019caf13-70d1-7314-afec-2218bd532bae" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-7039-a33b-ef913f0ab678" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-7039-a33b-ef913f0ab678_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-7039-a33b-ef913f0ab678" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-7039-a33b-ef913f0ab678_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-78a1-ad58-228db4c3d618" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-7039-a33b-ef913f0ab678" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-78a1-ad58-228db4c3d618" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7e21-a091-bf9b9192f870" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-78a1-ad58-228db4c3d618" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7e21-a091-bf9b9192f870" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7270-850a-6a6cddc8aed2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable_019caf13-70d1-7314-afec-2218bd532bae" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7270-850a-6a6cddc8aed2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7270-850a-6a6cddc8aed2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7270-850a-6a6cddc8aed2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7270-850a-6a6cddc8aed2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7ca3-af68-2d30c1db63eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-7270-850a-6a6cddc8aed2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7ca3-af68-2d30c1db63eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-73a7-9024-00921740d13a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7ca3-af68-2d30c1db63eb" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-73a7-9024-00921740d13a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d1-7942-a162-6f39abac00fc" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-7ca3-af68-2d30c1db63eb" xlink:to="loc_ally_OtherLoansMember_019caf13-70d1-7942-a162-6f39abac00fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7b3c-bd25-a7e37faeb60d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesTable_019caf13-70d1-7314-afec-2218bd532bae" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7b3c-bd25-a7e37faeb60d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7b3c-bd25-a7e37faeb60d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7b3c-bd25-a7e37faeb60d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7b3c-bd25-a7e37faeb60d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-77db-878e-a958655b409b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7b3c-bd25-a7e37faeb60d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-77db-878e-a958655b409b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7718-b679-c03f0b5cb320" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-77db-878e-a958655b409b" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7718-b679-c03f0b5cb320" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorProceedsFromNewTransfers_019caf13-70d1-7a7d-b22e-ab4d29282da3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowsBetweenTransfereeAndTransferorProceedsFromNewTransfers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:to="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorProceedsFromNewTransfers_019caf13-70d1-7a7d-b22e-ab4d29282da3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorServicingFees_019caf13-70d1-70e4-ae7f-aabf5e19af18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowsBetweenTransfereeAndTransferorServicingFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:to="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorServicingFees_019caf13-70d1-70e4-ae7f-aabf5e19af18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowsBetweenTransferorAndTransfereeBeneficialInterest_019caf13-70d1-7beb-87ce-553c5be48487" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowsBetweenTransferorAndTransfereeBeneficialInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:to="loc_us-gaap_CashFlowsBetweenTransferorAndTransfereeBeneficialInterest_019caf13-70d1-7beb-87ce-553c5be48487" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorReceiptsOnInterestsThatContinueToBeHeldOther_019caf13-70d1-79ba-b661-ad7fb6372b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowsBetweenTransfereeAndTransferorReceiptsOnInterestsThatContinueToBeHeldOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems_019caf13-70d1-765f-9a06-056d694086f4" xlink:to="loc_us-gaap_CashFlowsBetweenTransfereeAndTransferorReceiptsOnInterestsThatContinueToBeHeldOther_019caf13-70d1-79ba-b661-ad7fb6372b9e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofQuantitativeInformationandNetCreditLossesaboutSecuritizedandOtherFinancialAssetsManagedTogetherDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#SecuritizationsandVariableInterestEntitiesScheduleofQuantitativeInformationandNetCreditLossesaboutSecuritizedandOtherFinancialAssetsManagedTogetherDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/SecuritizationsandVariableInterestEntitiesScheduleofQuantitativeInformationandNetCreditLossesaboutSecuritizedandOtherFinancialAssetsManagedTogetherDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_019caf13-70d1-7a8d-90af-dbc6b7d73920" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_019caf13-70d1-7a8d-90af-dbc6b7d73920" xlink:to="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis_019caf13-70d1-722c-8ff2-efb02b44c966" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis_019caf13-70d1-722c-8ff2-efb02b44c966" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-722c-8ff2-efb02b44c966_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis_019caf13-70d1-722c-8ff2-efb02b44c966" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-722c-8ff2-efb02b44c966_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-71ad-b4ba-71c312d9a454" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis_019caf13-70d1-722c-8ff2-efb02b44c966" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-71ad-b4ba-71c312d9a454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OffBalanceSheetSecuritizationEntitiesMember_019caf13-70d1-7b11-9b69-3fca47864370" xlink:href="ally-20260331.xsd#ally_OffBalanceSheetSecuritizationEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-71ad-b4ba-71c312d9a454" xlink:to="loc_ally_OffBalanceSheetSecuritizationEntitiesMember_019caf13-70d1-7b11-9b69-3fca47864370" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_WholeLoanSalesMember_019caf13-70d1-7ab7-89e8-51334cb07e1d" xlink:href="ally-20260331.xsd#ally_WholeLoanSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementInTransferredFinancialAssetsTransferOrTransfereeDomain_019caf13-70d1-71ad-b4ba-71c312d9a454" xlink:to="loc_ally_WholeLoanSalesMember_019caf13-70d1-7ab7-89e8-51334cb07e1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-764c-b51e-f55d8fababcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-764c-b51e-f55d8fababcb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-764c-b51e-f55d8fababcb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-764c-b51e-f55d8fababcb" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-764c-b51e-f55d8fababcb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-779b-a8c9-2b9e39c557a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-70d1-764c-b51e-f55d8fababcb" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-779b-a8c9-2b9e39c557a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-76e4-94a4-347cee51642b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-779b-a8c9-2b9e39c557a4" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-70d1-76e4-94a4-347cee51642b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-70d1-719b-9662-9a30f27aaef3" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-70d1-779b-a8c9-2b9e39c557a4" xlink:to="loc_ally_OtherLoansMember_019caf13-70d1-719b-9662-9a30f27aaef3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7bff-b326-c1462181e97a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7bff-b326-c1462181e97a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7bff-b326-c1462181e97a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7bff-b326-c1462181e97a" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7bff-b326-c1462181e97a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-79ba-8ab1-a203594f3581" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7bff-b326-c1462181e97a" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-79ba-8ab1-a203594f3581" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7213-b312-0137aff0c097" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-79ba-8ab1-a203594f3581" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7213-b312-0137aff0c097" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-72c7-a4d2-6f9972af8d36" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_019caf13-70d1-79e1-b051-7b3bae82698d" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-72c7-a4d2-6f9972af8d36" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-72c7-a4d2-6f9972af8d36_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-72c7-a4d2-6f9972af8d36" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-72c7-a4d2-6f9972af8d36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-73fb-a0d9-d07fe377ba50" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019caf13-70d1-72c7-a4d2-6f9972af8d36" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-73fb-a0d9-d07fe377ba50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7cb7-a2a2-0eab33735d46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019caf13-70d1-73fb-a0d9-d07fe377ba50" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_019caf13-70d1-7cb7-a2a2-0eab33735d46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrincipalAmountOutstandingOnLoansManagedAndSecuritized_019caf13-70d1-7338-880a-423e97f72d99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrincipalAmountOutstandingOnLoansManagedAndSecuritized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_019caf13-70d1-7a8d-90af-dbc6b7d73920" xlink:to="loc_us-gaap_PrincipalAmountOutstandingOnLoansManagedAndSecuritized_019caf13-70d1-7338-880a-423e97f72d99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherDelinquentAmountAtEndOfPeriod_019caf13-70d1-7565-b742-fa2e43f233bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherDelinquentAmountAtEndOfPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_019caf13-70d1-7a8d-90af-dbc6b7d73920" xlink:to="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherDelinquentAmountAtEndOfPeriod_019caf13-70d1-7565-b742-fa2e43f233bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement_019caf13-70d1-7c22-a10d-dcb2c86ac5ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerecognizedAssetsSecuritizedOrAssetbackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_019caf13-70d1-7a8d-90af-dbc6b7d73920" xlink:to="loc_us-gaap_NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement_019caf13-70d1-7c22-a10d-dcb2c86ac5ac" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/OtherAssetsNarrativeDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#OtherAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/OtherAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-73b8-b930-cd439964ae75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-73b8-b930-cd439964ae75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-70d1-7e7c-ad50-23b63fa1f000" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-73b8-b930-cd439964ae75" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-70d1-7e7c-ad50-23b63fa1f000" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7e7c-ad50-23b63fa1f000_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-70d1-7e7c-ad50-23b63fa1f000" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7e7c-ad50-23b63fa1f000_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7ba9-80ae-ed7900931711" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-70d1-7e7c-ad50-23b63fa1f000" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7ba9-80ae-ed7900931711" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-70d1-780b-b2e9-8b9234bee44c" xlink:href="ally-20260331.xsd#ally_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7ba9-80ae-ed7900931711" xlink:to="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-70d1-780b-b2e9-8b9234bee44c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019caf13-70d1-7a38-b93e-ab0ddb830bda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-73b8-b930-cd439964ae75" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019caf13-70d1-7a38-b93e-ab0ddb830bda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019caf13-70d1-7a38-b93e-ab0ddb830bda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019caf13-70d1-7a38-b93e-ab0ddb830bda" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019caf13-70d1-7a38-b93e-ab0ddb830bda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019caf13-70d1-7e57-af87-6133a67c470c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019caf13-70d1-7a38-b93e-ab0ddb830bda" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019caf13-70d1-7e57-af87-6133a67c470c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember_019caf13-70d1-7cdf-976a-d94492e0314e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019caf13-70d1-7e57-af87-6133a67c470c" xlink:to="loc_us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember_019caf13-70d1-7cdf-976a-d94492e0314e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019caf13-70d1-7f52-ab89-07040ff149d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-73b8-b930-cd439964ae75" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019caf13-70d1-7f52-ab89-07040ff149d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019caf13-70d1-7f52-ab89-07040ff149d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019caf13-70d1-7f52-ab89-07040ff149d2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019caf13-70d1-7f52-ab89-07040ff149d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019caf13-70d1-7f2d-9534-9f1c50254dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019caf13-70d1-7f52-ab89-07040ff149d2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019caf13-70d1-7f2d-9534-9f1c50254dc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AllyCreditCardMember_019caf13-70d1-795a-8cb5-8cec3fd12ab6" xlink:href="ally-20260331.xsd#ally_AllyCreditCardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019caf13-70d1-7f2d-9534-9f1c50254dc1" xlink:to="loc_ally_AllyCreditCardMember_019caf13-70d1-795a-8cb5-8cec3fd12ab6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestments_019caf13-70d1-7e28-85b7-27c96ceb215a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestments_019caf13-70d1-7e28-85b7-27c96ceb215a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualifiedAffordableHousingProjectInvestmentsCommitment_019caf13-70d1-74c4-bc68-568037c8ab45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_QualifiedAffordableHousingProjectInvestmentsCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_us-gaap_QualifiedAffordableHousingProjectInvestmentsCommitment_019caf13-70d1-74c4-bc68-568037c8ab45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InvestmentProgramProportionalAmortizationMethodElectedCommitmentPeriodToBePaid_019caf13-70d1-720a-a9f5-509b17cb3e03" xlink:href="ally-20260331.xsd#ally_InvestmentProgramProportionalAmortizationMethodElectedCommitmentPeriodToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_ally_InvestmentProgramProportionalAmortizationMethodElectedCommitmentPeriodToBePaid_019caf13-70d1-720a-a9f5-509b17cb3e03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_019caf13-70d1-7b65-98c8-e4d6098af8ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_019caf13-70d1-7b65-98c8-e4d6098af8ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillTransfers_019caf13-70d1-7738-bac6-576cb00f316f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillTransfers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7fc2-92b8-539a00d8ec62" xlink:to="loc_us-gaap_GoodwillTransfers_019caf13-70d1-7738-bac6-576cb00f316f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/OtherAssetsScheduleofGoodwillDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#OtherAssetsScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/OtherAssetsScheduleofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7733-be3c-86e136f53c98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-78ab-b1a0-97145578651d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7733-be3c-86e136f53c98" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-78ab-b1a0-97145578651d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-70d1-75bb-8185-2d43c33b98f6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-78ab-b1a0-97145578651d" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-70d1-75bb-8185-2d43c33b98f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-70d1-75bb-8185-2d43c33b98f6_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-70d1-75bb-8185-2d43c33b98f6" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-70d1-75bb-8185-2d43c33b98f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7b6e-912a-06c5b1c9106d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-70d1-75bb-8185-2d43c33b98f6" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7b6e-912a-06c5b1c9106d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf13-70d1-7f55-b89a-30d6476e2cbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7b6e-912a-06c5b1c9106d" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf13-70d1-7f55-b89a-30d6476e2cbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-70d1-73a5-8464-ec502554b2b9" xlink:href="ally-20260331.xsd#ally_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-70d1-7b6e-912a-06c5b1c9106d" xlink:to="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-70d1-73a5-8464-ec502554b2b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-70d1-7f01-9566-1a53b420a8fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-78ab-b1a0-97145578651d" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-70d1-7f01-9566-1a53b420a8fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-70d1-7f01-9566-1a53b420a8fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-70d1-7f01-9566-1a53b420a8fc" xlink:to="loc_us-gaap_SegmentDomain_019caf13-70d1-7f01-9566-1a53b420a8fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-70d1-79ea-8f14-04b6cd10ca75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-70d1-7f01-9566-1a53b420a8fc" xlink:to="loc_us-gaap_SegmentDomain_019caf13-70d1-79ea-8f14-04b6cd10ca75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-70d1-7e9d-b69e-c9722d6eab26" xlink:href="ally-20260331.xsd#ally_AutomotiveFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-70d1-79ea-8f14-04b6cd10ca75" xlink:to="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-70d1-7e9d-b69e-c9722d6eab26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InsuranceOperationsSegmentMember_019caf13-70d1-7bf5-b8d6-e68711d6f14e" xlink:href="ally-20260331.xsd#ally_InsuranceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-70d1-79ea-8f14-04b6cd10ca75" xlink:to="loc_ally_InsuranceOperationsSegmentMember_019caf13-70d1-7bf5-b8d6-e68711d6f14e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019caf13-70d1-71af-87ed-216d23dd912c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf13-70d1-78ab-b1a0-97145578651d" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019caf13-70d1-71af-87ed-216d23dd912c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019caf13-70d1-71af-87ed-216d23dd912c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019caf13-70d1-71af-87ed-216d23dd912c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019caf13-70d1-71af-87ed-216d23dd912c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019caf13-70d1-7937-886b-9b2be7462525" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019caf13-70d1-71af-87ed-216d23dd912c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019caf13-70d1-7937-886b-9b2be7462525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AllyInvestMember_019caf13-70d1-7533-ab53-a508077e9b5a" xlink:href="ally-20260331.xsd#ally_AllyInvestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019caf13-70d1-7937-886b-9b2be7462525" xlink:to="loc_ally_AllyInvestMember_019caf13-70d1-7533-ab53-a508077e9b5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_019caf13-70d1-76d2-beca-86a117d8d060" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf13-70d1-7733-be3c-86e136f53c98" xlink:to="loc_us-gaap_GoodwillRollForward_019caf13-70d1-76d2-beca-86a117d8d060" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019caf13-70d1-78f4-bbea-64aa1ea60c54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019caf13-70d1-76d2-beca-86a117d8d060" xlink:to="loc_us-gaap_Goodwill_019caf13-70d1-78f4-bbea-64aa1ea60c54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_019caf13-70d1-7130-80ec-5874eb8304dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019caf13-70d1-76d2-beca-86a117d8d060" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_019caf13-70d1-7130-80ec-5874eb8304dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillTransfers_019caf13-70d1-74aa-9660-520692b4778b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillTransfers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019caf13-70d1-76d2-beca-86a117d8d060" xlink:to="loc_us-gaap_GoodwillTransfers_019caf13-70d1-74aa-9660-520692b4778b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019caf13-70d1-778f-8693-ed0a19e1239c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DebtScheduleofShorttermDebtDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DebtScheduleofShorttermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DebtScheduleofShorttermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable_019caf13-70d1-77b6-9380-b3a4a7736681" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:to="loc_us-gaap_ScheduleOfShortTermDebtTable_019caf13-70d1-77b6-9380-b3a4a7736681" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-70d1-7c88-a423-f2ca6bad430c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_019caf13-70d1-77b6-9380-b3a4a7736681" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-70d1-7c88-a423-f2ca6bad430c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7c88-a423-f2ca6bad430c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-70d1-7c88-a423-f2ca6bad430c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7c88-a423-f2ca6bad430c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7a68-b5d2-b55f5476ace6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-70d1-7c88-a423-f2ca6bad430c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7a68-b5d2-b55f5476ace6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-781a-b4c2-17e0565fadec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7a68-b5d2-b55f5476ace6" xlink:to="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-781a-b4c2-17e0565fadec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019caf13-70d1-711a-ab8e-902b1ab1370d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-70d1-7a68-b5d2-b55f5476ace6" xlink:to="loc_us-gaap_SecuredDebtMember_019caf13-70d1-711a-ab8e-902b1ab1370d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_019caf13-70d1-7787-9f6e-6a8892ba81da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_019caf13-70d1-77b6-9380-b3a4a7736681" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_019caf13-70d1-7787-9f6e-6a8892ba81da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-7787-9f6e-6a8892ba81da_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_019caf13-70d1-7787-9f6e-6a8892ba81da" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-7787-9f6e-6a8892ba81da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-75ee-a273-71f05837d856" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_019caf13-70d1-7787-9f6e-6a8892ba81da" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-75ee-a273-71f05837d856" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaturityUpTo30DaysMember_019caf13-70d1-7b60-a1e4-521c9a53a2c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MaturityUpTo30DaysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-75ee-a273-71f05837d856" xlink:to="loc_us-gaap_MaturityUpTo30DaysMember_019caf13-70d1-7b60-a1e4-521c9a53a2c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_Maturity31To60DaysMember_019caf13-70d1-7265-9279-3a417eba6e0c" xlink:href="ally-20260331.xsd#ally_Maturity31To60DaysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_019caf13-70d1-75ee-a273-71f05837d856" xlink:to="loc_ally_Maturity31To60DaysMember_019caf13-70d1-7265-9279-3a417eba6e0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d1-736e-b6df-f5a371d678c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_019caf13-70d1-77b6-9380-b3a4a7736681" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d1-736e-b6df-f5a371d678c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d1-736e-b6df-f5a371d678c4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d1-736e-b6df-f5a371d678c4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d1-736e-b6df-f5a371d678c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d1-74e6-a5f1-69034e168c67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-70d1-736e-b6df-f5a371d678c4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d1-74e6-a5f1-69034e168c67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-70d1-76fc-8215-03f945a86bc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-70d1-74e6-a5f1-69034e168c67" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-70d1-76fc-8215-03f945a86bc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate_019caf13-70d1-7923-a00a-f1c367cf91dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate_019caf13-70d1-7923-a00a-f1c367cf91dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchase_019caf13-70d1-7d8b-bda7-e7e69257bc54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchase_019caf13-70d1-7d8b-bda7-e7e69257bc54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_019caf13-70d1-7f9d-8b9c-75eed795ab8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:to="loc_us-gaap_ShortTermBorrowings_019caf13-70d1-7f9d-8b9c-75eed795ab8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseFairValueOfCollateral_019caf13-70d1-7b05-b5ca-575c58bfe749" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseFairValueOfCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_019caf13-70d1-70fd-9029-6875d1c9a08d" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseFairValueOfCollateral_019caf13-70d1-7b05-b5ca-575c58bfe749" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DebtScheduleofLongtermDebtDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DebtScheduleofLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DebtScheduleofLongtermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7769-98a2-9af7c21a6272" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:to="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7769-98a2-9af7c21a6272" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-774e-9960-1056cdae1bb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7769-98a2-9af7c21a6272" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-774e-9960-1056cdae1bb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-774e-9960-1056cdae1bb0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-774e-9960-1056cdae1bb0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-774e-9960-1056cdae1bb0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76f6-97a5-78c665f33fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-774e-9960-1056cdae1bb0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76f6-97a5-78c665f33fa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-7437-aa36-1b42d70ee313" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76f6-97a5-78c665f33fa0" xlink:to="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-7437-aa36-1b42d70ee313" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019caf13-70d1-7592-b6cb-e712c059bb28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76f6-97a5-78c665f33fa0" xlink:to="loc_us-gaap_SecuredDebtMember_019caf13-70d1-7592-b6cb-e712c059bb28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019d4279-0495-774a-b516-67836c88d255" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76f6-97a5-78c665f33fa0" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019d4279-0495-774a-b516-67836c88d255" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis_019d4279-0495-712d-9c80-74b86d93fbf0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7769-98a2-9af7c21a6272" xlink:to="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis_019d4279-0495-712d-9c80-74b86d93fbf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain_019d4279-0495-712d-9c80-74b86d93fbf0_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis_019d4279-0495-712d-9c80-74b86d93fbf0" xlink:to="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain_019d4279-0495-712d-9c80-74b86d93fbf0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain_019d4279-0495-78f9-a997-9802cc2eb28a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis_019d4279-0495-712d-9c80-74b86d93fbf0" xlink:to="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain_019d4279-0495-78f9-a997-9802cc2eb28a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_FederalHomeLoanBankOfPittsburghMember_019d4279-0495-796d-9eba-b2d3a397a10b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_FederalHomeLoanBankOfPittsburghMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankStateDomain_019d4279-0495-78f9-a997-9802cc2eb28a" xlink:to="loc_srt_FederalHomeLoanBankOfPittsburghMember_019d4279-0495-796d-9eba-b2d3a397a10b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LongTermDebtCurrentMaturitiesNetOfOriginalIssueDiscount_019dac9d-56b1-772e-ac10-9ff1577b86f3" xlink:href="ally-20260331.xsd#ally_LongTermDebtCurrentMaturitiesNetOfOriginalIssueDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:to="loc_ally_LongTermDebtCurrentMaturitiesNetOfOriginalIssueDiscount_019dac9d-56b1-772e-ac10-9ff1577b86f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019caf13-70d1-71eb-8797-ade336c18ca2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:to="loc_us-gaap_LongTermDebtCurrent_019caf13-70d1-71eb-8797-ade336c18ca2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019caf13-70d1-7686-9a4a-54d623cb9f58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019caf13-70d1-7686-9a4a-54d623cb9f58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019caf13-70d1-7319-8041-676e14708a52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7f34-be6d-5098465295f1" xlink:to="loc_us-gaap_LongTermDebt_019caf13-70d1-7319-8041-676e14708a52" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DebtScheduleofRemainingMaturityofLongtermDebtDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DebtScheduleofRemainingMaturityofLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DebtScheduleofRemainingMaturityofLongtermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7efc-8b92-f55cb86d2990" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7efc-8b92-f55cb86d2990" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019caf13-70d1-751d-a8b1-49dcbdb325c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7efc-8b92-f55cb86d2990" xlink:to="loc_us-gaap_DebtInstrumentAxis_019caf13-70d1-751d-a8b1-49dcbdb325c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-751d-a8b1-49dcbdb325c9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-70d1-751d-a8b1-49dcbdb325c9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-751d-a8b1-49dcbdb325c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-7657-a766-14e0357035ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-70d1-751d-a8b1-49dcbdb325c9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-7657-a766-14e0357035ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMember_019caf13-70d1-709a-8fc0-22dae98f09ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-7657-a766-14e0357035ee" xlink:to="loc_us-gaap_LongTermDebtMember_019caf13-70d1-709a-8fc0-22dae98f09ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OriginalIssueDiscountMember_019caf13-70d1-733c-a4fd-8411576e22aa" xlink:href="ally-20260331.xsd#ally_OriginalIssueDiscountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-70d1-7657-a766-14e0357035ee" xlink:to="loc_ally_OriginalIssueDiscountMember_019caf13-70d1-733c-a4fd-8411576e22aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-76c8-a675-a9e9674ed440" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7efc-8b92-f55cb86d2990" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-76c8-a675-a9e9674ed440" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76c8-a675-a9e9674ed440_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-76c8-a675-a9e9674ed440" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-76c8-a675-a9e9674ed440_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-77eb-b428-cfeeee9af978" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-70d1-76c8-a675-a9e9674ed440" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-77eb-b428-cfeeee9af978" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-76f7-8259-39d04d5f7cee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-77eb-b428-cfeeee9af978" xlink:to="loc_us-gaap_UnsecuredDebtMember_019caf13-70d1-76f7-8259-39d04d5f7cee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019caf13-70d1-72e7-9f6a-06b303be19ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-70d1-77eb-b428-cfeeee9af978" xlink:to="loc_us-gaap_SecuredDebtMember_019caf13-70d1-72e7-9f6a-06b303be19ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019caf13-70d1-7abc-a29c-b12c7aba157d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019caf13-70d1-7efc-8b92-f55cb86d2990" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019caf13-70d1-7abc-a29c-b12c7aba157d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7abc-a29c-b12c7aba157d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019caf13-70d1-7abc-a29c-b12c7aba157d" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7abc-a29c-b12c7aba157d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019caf13-70d1-7abc-a29c-b12c7aba157d" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019caf13-70d1-7d60-9e3c-c219e387b52f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019caf13-70d1-7d60-9e3c-c219e387b52f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019caf13-70d1-7bf4-ad3d-f185fd4cfd50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019caf13-70d1-7bf4-ad3d-f185fd4cfd50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019caf13-70d1-7985-b693-bf8ab1095b68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019caf13-70d1-7985-b693-bf8ab1095b68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodFourMember_019caf13-70d1-7b94-9416-e7cb02d6619a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodFourMember_019caf13-70d1-7b94-9416-e7cb02d6619a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodFiveMember_019caf13-70d1-785a-aa1a-7dc85165f6ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodFiveMember_019caf13-70d1-785a-aa1a-7dc85165f6ac" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtInstrumentRedemptionPeriodSixMember_019caf13-70d1-71fc-aeca-0bd01804f52b" xlink:href="ally-20260331.xsd#ally_DebtInstrumentRedemptionPeriodSixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019caf13-70d1-7d7d-aea6-a9569ace6587" xlink:to="loc_ally_DebtInstrumentRedemptionPeriodSixMember_019caf13-70d1-71fc-aeca-0bd01804f52b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019d4247-c18a-77b0-b3a6-30d9ef2698bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019d4247-c18a-77b0-b3a6-30d9ef2698bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LongTermDebtMaturityNetOfOriginalIssueDiscountRemainderOfFiscalYear_019dac8c-bdad-726a-9fd7-98c4529de138" xlink:href="ally-20260331.xsd#ally_LongTermDebtMaturityNetOfOriginalIssueDiscountRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_ally_LongTermDebtMaturityNetOfOriginalIssueDiscountRemainderOfFiscalYear_019dac8c-bdad-726a-9fd7-98c4529de138" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019caf13-70d1-7c2b-955b-e0df0aac1bf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019caf13-70d1-7c2b-955b-e0df0aac1bf7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019caf13-70d1-7e9e-aa7a-517063ab279f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019caf13-70d1-7e9e-aa7a-517063ab279f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019caf13-70d1-74ed-9ec3-eccf82bf8bf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019caf13-70d1-74ed-9ec3-eccf82bf8bf8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019caf13-70d1-7bc9-93aa-19174740af40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019caf13-70d1-7bc9-93aa-19174740af40" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LongTermDebtMaturityAfterYearFour_019d4249-0105-7f1c-b93d-d9447cea7edc" xlink:href="ally-20260331.xsd#ally_LongTermDebtMaturityAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_ally_LongTermDebtMaturityAfterYearFour_019d4249-0105-7f1c-b93d-d9447cea7edc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019caf13-70d1-75f5-ac46-51a07dc05e85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_LongTermDebt_019caf13-70d1-75f5-ac46-51a07dc05e85" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountCurrent_019caf13-70d1-7fad-8e60-852a1fd17455" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountCurrent_019caf13-70d1-7fad-8e60-852a1fd17455" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent_019caf13-70d1-7a5b-acc5-20ba648ba074" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent_019caf13-70d1-7a5b-acc5-20ba648ba074" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019caf13-70d1-740b-ba72-3b19ec63bcb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019caf13-70d1-7a14-98b4-46757a13a950" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019caf13-70d1-740b-ba72-3b19ec63bcb9" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DebtScheduleofPledgedAssetsRelatedtoSecuredBorrowingsandRepurchaseAgreementDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DebtScheduleofPledgedAssetsRelatedtoSecuredBorrowingsandRepurchaseAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DebtScheduleofPledgedAssetsRelatedtoSecuredBorrowingsandRepurchaseAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:href="ally-20260331.xsd#ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:to="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7626-adf2-f7d905ce9569" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7626-adf2-f7d905ce9569" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7626-adf2-f7d905ce9569_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7626-adf2-f7d905ce9569" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7626-adf2-f7d905ce9569_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7666-b3d6-7845d392bc6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-70d1-7626-adf2-f7d905ce9569" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7666-b3d6-7845d392bc6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7a8a-b945-84fc8141a72a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7666-b3d6-7845d392bc6a" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-70d1-7a8a-b945-84fc8141a72a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-7d1f-8e96-9de67903451e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-70d1-7666-b3d6-7845d392bc6a" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-70d1-7d1f-8e96-9de67903451e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7183-7d19-b191-24f833f82373" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7183-7d19-b191-24f833f82373" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7d19-b191-24f833f82373_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7183-7d19-b191-24f833f82373" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7d19-b191-24f833f82373_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7401-8723-1a7ef68b4cc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7183-7d19-b191-24f833f82373" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7401-8723-1a7ef68b4cc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-7183-7e75-8e51-fe85baf105dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7401-8723-1a7ef68b4cc4" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-7183-7e75-8e51-fe85baf105dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateLoanMember_019caf13-7183-7b44-a089-d093b4aa1d51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7183-7401-8723-1a7ef68b4cc4" xlink:to="loc_us-gaap_RealEstateLoanMember_019caf13-7183-7b44-a089-d093b4aa1d51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-7183-7f78-a0a7-506f10506f28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-7183-7f78-a0a7-506f10506f28" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7183-7f78-a0a7-506f10506f28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7183-7f78-a0a7-506f10506f28" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7183-7f78-a0a7-506f10506f28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7183-7cc4-b641-e19cfde95a31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7183-7f78-a0a7-506f10506f28" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7183-7cc4-b641-e19cfde95a31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_019caf13-7183-799e-b2bc-87c2df350ff7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7183-7cc4-b641-e19cfde95a31" xlink:to="loc_us-gaap_DebtSecuritiesMember_019caf13-7183-799e-b2bc-87c2df350ff7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019caf13-7183-7263-8b1d-be3b653eb701" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_DebtInstrumentAxis_019caf13-7183-7263-8b1d-be3b653eb701" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-7263-8b1d-be3b653eb701_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-7183-7263-8b1d-be3b653eb701" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-7263-8b1d-be3b653eb701_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-705c-9252-85a14e6a2a59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-7183-7263-8b1d-be3b653eb701" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-705c-9252-85a14e6a2a59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CreditLinkedNotesMember_019caf13-7183-7357-868a-b42760bbf1b2" xlink:href="ally-20260331.xsd#ally_CreditLinkedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-705c-9252-85a14e6a2a59" xlink:to="loc_ally_CreditLinkedNotesMember_019caf13-7183-7357-868a-b42760bbf1b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_PledgedAssetsForFederalHomeLoanBankMember_019caf13-7183-7c71-9738-e379fd48f2ed" xlink:href="ally-20260331.xsd#ally_PledgedAssetsForFederalHomeLoanBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-705c-9252-85a14e6a2a59" xlink:to="loc_ally_PledgedAssetsForFederalHomeLoanBankMember_019caf13-7183-7c71-9738-e379fd48f2ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_PledgedAssetsForFederalReserveBankMember_019caf13-7183-7e23-9fd8-bac68d4abd19" xlink:href="ally-20260331.xsd#ally_PledgedAssetsForFederalReserveBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7183-705c-9252-85a14e6a2a59" xlink:to="loc_ally_PledgedAssetsForFederalReserveBankMember_019caf13-7183-7e23-9fd8-bac68d4abd19" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_019caf13-7183-774e-9344-8c57f597012e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_PledgedStatusAxis_019caf13-7183-774e-9344-8c57f597012e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019caf13-7183-774e-9344-8c57f597012e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_019caf13-7183-774e-9344-8c57f597012e" xlink:to="loc_us-gaap_PledgedStatusDomain_019caf13-7183-774e-9344-8c57f597012e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019caf13-7183-77e8-a97a-f9dfde171fe3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_019caf13-7183-774e-9344-8c57f597012e" xlink:to="loc_us-gaap_PledgedStatusDomain_019caf13-7183-77e8-a97a-f9dfde171fe3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralMember_019caf13-7183-729b-a5b8-3066763e3152" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetPledgedAsCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_019caf13-7183-77e8-a97a-f9dfde171fe3" xlink:to="loc_us-gaap_AssetPledgedAsCollateralMember_019caf13-7183-729b-a5b8-3066763e3152" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-7183-73d2-93d3-460452336501" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ally_ScheduleOfPledgedAssetsRelatedToSecuredBorrowingsTable_019caf13-70d1-7c3e-a494-e3ab104797be" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-7183-73d2-93d3-460452336501" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-7183-73d2-93d3-460452336501_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-7183-73d2-93d3-460452336501" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-7183-73d2-93d3-460452336501_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-7183-72bc-966a-327c5676a950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_019caf13-7183-73d2-93d3-460452336501" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-7183-72bc-966a-327c5676a950" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019caf13-7183-7781-9238-8bb2d00a3385" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_019caf13-7183-72bc-966a-327c5676a950" xlink:to="loc_us-gaap_SecuredDebtMember_019caf13-7183-7781-9238-8bb2d00a3385" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCollateralAmount_019caf13-7183-7211-8a78-8376a01d4890" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCollateralAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:to="loc_us-gaap_DebtInstrumentCollateralAmount_019caf13-7183-7211-8a78-8376a01d4890" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_SecuredDebtLongTermAndShortTermCombinedAmount_019caf13-7183-749f-88ee-f49af3177fb6" xlink:href="ally-20260331.xsd#ally_SecuredDebtLongTermAndShortTermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:to="loc_ally_SecuredDebtLongTermAndShortTermCombinedAmount_019caf13-7183-749f-88ee-f49af3177fb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7183-7bbc-8fb9-eaffb62db549" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7183-7bbc-8fb9-eaffb62db549" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_019caf13-7183-735f-951a-e27af40dc469" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems_019caf13-7183-718a-b920-9877f893bc70" xlink:to="loc_us-gaap_ShortTermBorrowings_019caf13-7183-735f-951a-e27af40dc469" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/PreferredStockDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#PreferredStockDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/PreferredStockDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7232-7e1c-a3c3-ffb104915cd0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7232-7e1c-a3c3-ffb104915cd0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019caf13-7232-7972-b43f-1ac0b9005d83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7232-7e1c-a3c3-ffb104915cd0" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019caf13-7232-7972-b43f-1ac0b9005d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7232-7972-b43f-1ac0b9005d83_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7232-7972-b43f-1ac0b9005d83" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7232-7972-b43f-1ac0b9005d83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7232-79d4-a281-ac6589af3117" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7232-7972-b43f-1ac0b9005d83" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7232-79d4-a281-ac6589af3117" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7232-7de3-8417-7119211d4fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7232-79d4-a281-ac6589af3117" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7232-7de3-8417-7119211d4fe9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_SeriesBPreferredStockPriorToMay152026Member_019caf13-7232-70c6-91d1-af13629a4143" xlink:href="ally-20260331.xsd#ally_SeriesBPreferredStockPriorToMay152026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7232-7de3-8417-7119211d4fe9" xlink:to="loc_ally_SeriesBPreferredStockPriorToMay152026Member_019caf13-7232-70c6-91d1-af13629a4143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_SeriesBPreferredStockOnAndAfterMay152026Member_019caf13-7232-7855-8fe8-355ccf5ccf32" xlink:href="ally-20260331.xsd#ally_SeriesBPreferredStockOnAndAfterMay152026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7232-7de3-8417-7119211d4fe9" xlink:to="loc_ally_SeriesBPreferredStockOnAndAfterMay152026Member_019caf13-7232-7855-8fe8-355ccf5ccf32" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7232-78d8-9442-02d0dcf02b90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesCPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7232-79d4-a281-ac6589af3117" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7232-78d8-9442-02d0dcf02b90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_SeriesCPreferredStockPriorToMay152028Member_019caf13-7232-77d7-ad9b-88ed9252ca75" xlink:href="ally-20260331.xsd#ally_SeriesCPreferredStockPriorToMay152028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7232-78d8-9442-02d0dcf02b90" xlink:to="loc_ally_SeriesCPreferredStockPriorToMay152028Member_019caf13-7232-77d7-ad9b-88ed9252ca75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_SeriesCPreferredStockOnAndAfterMay152028Member_019caf13-7232-7877-bca4-b3d1f7057800" xlink:href="ally-20260331.xsd#ally_SeriesCPreferredStockOnAndAfterMay152028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7232-78d8-9442-02d0dcf02b90" xlink:to="loc_ally_SeriesCPreferredStockOnAndAfterMay152028Member_019caf13-7232-7877-bca4-b3d1f7057800" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019dbf1d-2051-7271-b91f-ae1e8961a53c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7232-7e1c-a3c3-ffb104915cd0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019dbf1d-2051-7271-b91f-ae1e8961a53c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dbf1d-2051-7271-b91f-ae1e8961a53c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dbf1d-2051-7271-b91f-ae1e8961a53c" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dbf1d-2051-7271-b91f-ae1e8961a53c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dbf1d-2051-7fe4-9d74-c030b6a2abd7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dbf1d-2051-7271-b91f-ae1e8961a53c" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dbf1d-2051-7fe4-9d74-c030b6a2abd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019dbf1d-2051-7902-9c02-e6900ad2645b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019dbf1d-2051-7fe4-9d74-c030b6a2abd7" xlink:to="loc_us-gaap_SubsequentEventMember_019dbf1d-2051-7902-9c02-e6900ad2645b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019caf13-7232-7aef-a94a-e853861d74cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockValue_019caf13-7232-7aef-a94a-e853861d74cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019caf13-7232-7a51-b467-0116d9f34440" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019caf13-7232-7a51-b467-0116d9f34440" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreference_019caf13-7232-7cda-9420-cbd31bfc0db5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockLiquidationPreference"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockLiquidationPreference_019caf13-7232-7cda-9420-cbd31bfc0db5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_019caf13-7232-7029-90e1-2e04421ebd62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_019caf13-7232-7029-90e1-2e04421ebd62" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019caf13-7232-7c56-8642-85ee2ad80af1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019caf13-7232-7c56-8642-85ee2ad80af1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019caf13-7232-7a71-afcb-669ca52bfa30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019caf13-7232-7a71-afcb-669ca52bfa30" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_019caf13-7232-75d6-8d7c-8f60470d812f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7232-7b2f-8100-6eafef735345" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_019caf13-7232-75d6-8d7c-8f60470d812f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7e19-b8a7-08ec3bf89d5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-7c40-bffc-09035dab18ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7e19-b8a7-08ec3bf89d5f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-7c40-bffc-09035dab18ee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79cd-9a1c-ca506e525915" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-7c40-bffc-09035dab18ee" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79cd-9a1c-ca506e525915" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7184-79cd-9a1c-ca506e525915_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79cd-9a1c-ca506e525915" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7184-79cd-9a1c-ca506e525915_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7184-71a8-93a2-2eaf35dbfe99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79cd-9a1c-ca506e525915" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7184-71a8-93a2-2eaf35dbfe99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-71a8-93a2-2eaf35dbfe99" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019caf13-7184-760d-9ca5-5c2b1699ded3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019caf13-7184-760d-9ca5-5c2b1699ded3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember_019caf13-7184-76c4-a050-c358bc8a08d6" xlink:href="ally-20260331.xsd#ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:to="loc_ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember_019caf13-7184-76c4-a050-c358bc8a08d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AccumulatedForeignCurrencyAdjustmentAndNetGainLossFromInvestmentHedgesParentMember_019caf13-7184-7655-9413-7b0e7c471c60" xlink:href="ally-20260331.xsd#ally_AccumulatedForeignCurrencyAdjustmentAndNetGainLossFromInvestmentHedgesParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:to="loc_ally_AccumulatedForeignCurrencyAdjustmentAndNetGainLossFromInvestmentHedgesParentMember_019caf13-7184-7655-9413-7b0e7c471c60" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019caf13-7184-7392-9445-8af81760d0cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf13-7184-7564-8d46-bb45860a8843" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019caf13-7184-7392-9445-8af81760d0cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019caf13-7184-7a33-aad1-1492845c504d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7e19-b8a7-08ec3bf89d5f" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019caf13-7184-7a33-aad1-1492845c504d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019caf13-7184-7dc8-96bb-b6cf134bb81c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019caf13-7184-7a33-aad1-1492845c504d" xlink:to="loc_us-gaap_StockholdersEquity_019caf13-7184-7dc8-96bb-b6cf134bb81c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7184-7046-9de9-b7c68ed90e4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019caf13-7184-7a33-aad1-1492845c504d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7184-7046-9de9-b7c68ed90e4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019caf13-7184-79d0-8282-7c26b59047e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/AccumulatedOtherComprehensiveLossScheduleofReclassificationOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#AccumulatedOtherComprehensiveLossScheduleofReclassificationOutofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/AccumulatedOtherComprehensiveLossScheduleofReclassificationOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-717a-b7dc-99d7aa1961ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-717a-b7dc-99d7aa1961ef" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79e0-a576-2ae2f2223de7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf13-7184-717a-b7dc-99d7aa1961ef" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79e0-a576-2ae2f2223de7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7184-79e0-a576-2ae2f2223de7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79e0-a576-2ae2f2223de7" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7184-79e0-a576-2ae2f2223de7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf13-7184-79e0-a576-2ae2f2223de7" xlink:to="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019caf13-7184-7bf7-bb64-eb03de208eee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019caf13-7184-7bf7-bb64-eb03de208eee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember_019caf13-7184-77dd-9bf7-02bb29f2fdd6" xlink:href="ally-20260331.xsd#ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:to="loc_ally_AOCIAccumulatedGainLossDebtSecuritiesHeldToMaturityParentMember_019caf13-7184-77dd-9bf7-02bb29f2fdd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019caf13-7184-7b51-a978-cc2e1a19c1fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019caf13-7184-7b51-a978-cc2e1a19c1fb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AccumulatedNetGainLossFromInvestmentHedgesParentMember_019caf13-7184-7a47-93d8-c2c587eef89d" xlink:href="ally-20260331.xsd#ally_AccumulatedNetGainLossFromInvestmentHedgesParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:to="loc_ally_AccumulatedNetGainLossFromInvestmentHedgesParentMember_019caf13-7184-7a47-93d8-c2c587eef89d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019caf13-7184-7d13-9da7-f271146e6b48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf13-7184-7998-a019-e696dd969a1f" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019caf13-7184-7d13-9da7-f271146e6b48" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019caf13-7184-71c2-bb2d-fd1a10cc2db2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019caf13-7184-71c2-bb2d-fd1a10cc2db2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019caf13-7184-7a2b-869f-216112b00fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019caf13-7184-7a2b-869f-216112b00fe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019caf13-7184-7ce3-b14b-f564010d34ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019caf13-7184-7ce3-b14b-f564010d34ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019caf13-7184-7f0f-bc84-10e7504a84d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019caf13-7184-7f0f-bc84-10e7504a84d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019caf13-7184-7dd1-be73-d600c5ef4037" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019caf13-7184-7dd1-be73-d600c5ef4037" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019caf13-7184-7d4e-9ade-a3617c5beb09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019caf13-7184-7d4e-9ade-a3617c5beb09" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019caf13-7184-72b0-8b92-44f91013bc29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019caf13-7184-72b0-8b92-44f91013bc29" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019caf13-7184-78f5-b5b0-a745c605f365" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019caf13-7184-78f5-b5b0-a745c605f365" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7184-7bd7-852c-10732b5e531b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf13-7184-7cc0-ae7d-ff27ab74c0ac" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019caf13-7184-7bd7-852c-10732b5e531b" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/EarningsperCommonShareDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#EarningsperCommonShareDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/EarningsperCommonShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7184-7704-b287-77b881a5b4a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7184-7704-b287-77b881a5b4a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019caf13-7184-77ac-b7d9-2adf373753ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019caf13-7184-7704-b287-77b881a5b4a5" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019caf13-7184-77ac-b7d9-2adf373753ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7184-77ac-b7d9-2adf373753ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7184-77ac-b7d9-2adf373753ed" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7184-77ac-b7d9-2adf373753ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019caf13-7184-7c7f-b369-623d0d81478d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019caf13-7184-77ac-b7d9-2adf373753ed" xlink:to="loc_us-gaap_ClassOfStockDomain_019caf13-7184-7c7f-b369-623d0d81478d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7184-74d9-8183-18a9b4a37bf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7184-7c7f-b369-623d0d81478d" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_019caf13-7184-74d9-8183-18a9b4a37bf1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7184-73d9-9cda-f4c70087db16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesCPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019caf13-7184-7c7f-b369-623d0d81478d" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_019caf13-7184-73d9-9cda-f4c70087db16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_019caf13-7184-7662-a8b9-7a6004495160" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_019caf13-7184-7662-a8b9-7a6004495160" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_019caf13-7184-7256-aa8b-635921ca4f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendsIncomeStatementImpact"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_019caf13-7184-7256-aa8b-635921ca4f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic_019caf13-7184-7295-b339-23c66622e828" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic_019caf13-7184-7295-b339-23c66622e828" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019caf13-7184-70d9-8059-cdf6614e926f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019caf13-7184-70d9-8059-cdf6614e926f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019caf13-7184-7a70-946d-30e96b0ffd9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019caf13-7184-7a70-946d-30e96b0ffd9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019caf13-7184-7bcb-a25e-d14d4f2f9d67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019caf13-7184-7bcb-a25e-d14d4f2f9d67" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_019caf13-7184-76eb-89a0-a982cb9edd1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_019caf13-7184-76eb-89a0-a982cb9edd1b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_019caf13-7184-7fcc-8960-24d88caff13f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019caf13-7184-76eb-89a0-a982cb9edd1b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_019caf13-7184-7fcc-8960-24d88caff13f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019caf13-7184-7cd9-87eb-1c5559ea7810" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019caf13-7184-76eb-89a0-a982cb9edd1b" xlink:to="loc_us-gaap_EarningsPerShareBasic_019caf13-7184-7cd9-87eb-1c5559ea7810" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_019caf13-7184-76af-98b5-8ecd043d1848" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_019caf13-7184-76af-98b5-8ecd043d1848" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_019caf13-7184-70c5-adf9-e9d60d82158c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019caf13-7184-76af-98b5-8ecd043d1848" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_019caf13-7184-70c5-adf9-e9d60d82158c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019caf13-7184-7c84-b26c-59cac4a98e34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019caf13-7184-76af-98b5-8ecd043d1848" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019caf13-7184-7c84-b26c-59cac4a98e34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019d0050-dacb-794d-9b40-896b510d69a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019caf13-7184-7c2b-b7cb-5cd7902a623a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019d0050-dacb-794d-9b40-896b510d69a6" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/RegulatoryCapitalandOtherRegulatoryMattersScheduleofRegulatoryCapitalAmountandRatiosDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#RegulatoryCapitalandOtherRegulatoryMattersScheduleofRegulatoryCapitalAmountandRatiosDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/RegulatoryCapitalandOtherRegulatoryMattersScheduleofRegulatoryCapitalAmountandRatiosDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019caf13-7184-7f86-abee-454a7a0dfff4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019caf13-7184-7f86-abee-454a7a0dfff4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019caf13-7184-7b47-a69f-7b628659c8d8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019caf13-7184-7f86-abee-454a7a0dfff4" xlink:to="loc_dei_LegalEntityAxis_019caf13-7184-7b47-a69f-7b628659c8d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019caf13-7184-7b47-a69f-7b628659c8d8_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019caf13-7184-7b47-a69f-7b628659c8d8" xlink:to="loc_dei_EntityDomain_019caf13-7184-7b47-a69f-7b628659c8d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019caf13-7184-7e51-b029-40e1ae88c1a0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019caf13-7184-7b47-a69f-7b628659c8d8" xlink:to="loc_dei_EntityDomain_019caf13-7184-7e51-b029-40e1ae88c1a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AllyFinancialIncMember_019caf13-7184-75e4-947b-2f62a8dd8581" xlink:href="ally-20260331.xsd#ally_AllyFinancialIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019caf13-7184-7e51-b029-40e1ae88c1a0" xlink:to="loc_ally_AllyFinancialIncMember_019caf13-7184-75e4-947b-2f62a8dd8581" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AllyBankMember_019caf13-7184-7672-8270-d2a41568f525" xlink:href="ally-20260331.xsd#ally_AllyBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019caf13-7184-7e51-b029-40e1ae88c1a0" xlink:to="loc_ally_AllyBankMember_019caf13-7184-7672-8270-d2a41568f525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioCapitalAdequacyMinimum_019caf13-7184-7898-9533-f298766c35f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioCapitalAdequacyMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioCapitalAdequacyMinimum_019caf13-7184-7898-9533-f298766c35f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets_019caf13-7184-7f45-aa9e-bbb54e4309cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets_019caf13-7184-7f45-aa9e-bbb54e4309cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets_019caf13-7184-710b-a599-5729933bcf5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets_019caf13-7184-710b-a599-5729933bcf5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets_019caf13-7184-7850-93d1-b84ad5136175" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets_019caf13-7184-7850-93d1-b84ad5136175" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum_019caf13-7184-731a-9284-8f3888d5630d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum_019caf13-7184-731a-9284-8f3888d5630d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_BankingRegulationAccumulatedOtherComprehensiveLossesExcludedFromCommonEquityTier1RiskBasedCapital_019caf13-7184-7508-af42-150cf72b99ff" xlink:href="ally-20260331.xsd#ally_BankingRegulationAccumulatedOtherComprehensiveLossesExcludedFromCommonEquityTier1RiskBasedCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_ally_BankingRegulationAccumulatedOtherComprehensiveLossesExcludedFromCommonEquityTier1RiskBasedCapital_019caf13-7184-7508-af42-150cf72b99ff" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestBearingDomesticDepositBrokered_019caf13-7184-76f9-9fe3-6e53b5a3cafe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestBearingDomesticDepositBrokered"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_InterestBearingDomesticDepositBrokered_019caf13-7184-76f9-9fe3-6e53b5a3cafe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsBrokered_019caf13-7184-79f0-9786-701071421390" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsBrokered"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_PercentageOfInterestBearingDomesticDepositsToDepositsBrokered_019caf13-7184-79f0-9786-701071421390" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonEquityTierOneCapital_019caf13-7184-7705-aa1a-f770ae68c70f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonEquityTierOneCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_CommonEquityTierOneCapital_019caf13-7184-7705-aa1a-f770ae68c70f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonEquityTierOneCapitalRatio_019caf13-7184-7a4c-a243-7025c9f7d8af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonEquityTierOneCapitalRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_CommonEquityTierOneCapitalRatio_019caf13-7184-7a4c-a243-7025c9f7d8af" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioWellCapitalizedMinimum_019caf13-7184-71aa-96a7-ee489dbf481e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioWellCapitalizedMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioWellCapitalizedMinimum_019caf13-7184-71aa-96a7-ee489dbf481e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneRiskBasedCapital_019caf13-7184-783b-8720-65d4a8343eb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneRiskBasedCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneRiskBasedCapital_019caf13-7184-783b-8720-65d4a8343eb0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets_019caf13-7184-7635-8b09-ba6927cf8c64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets_019caf13-7184-7635-8b09-ba6927cf8c64" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets_019caf13-7184-75b0-872b-96349fb16f59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets_019caf13-7184-75b0-872b-96349fb16f59" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Capital_019caf13-7184-74dc-8665-b24285cfe9b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Capital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_Capital_019caf13-7184-74dc-8665-b24285cfe9b5" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalToRiskWeightedAssets_019caf13-7184-7ffa-a4cc-2d924658c611" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_CapitalToRiskWeightedAssets_019caf13-7184-7ffa-a4cc-2d924658c611" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets_019caf13-7184-7863-b4de-493f827c9c16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets_019caf13-7184-7863-b4de-493f827c9c16" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneLeverageCapital_019caf13-7184-707b-b0e0-09e8ff20b6f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneLeverageCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneLeverageCapital_019caf13-7184-707b-b0e0-09e8ff20b6f9" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneLeverageCapitalToAverageAssets_019caf13-7184-76ac-a2c9-0015fc7256c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneLeverageCapitalToAverageAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneLeverageCapitalToAverageAssets_019caf13-7184-76ac-a2c9-0015fc7256c0" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets_019caf13-7184-7cce-a030-b0d60283e4fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019caf13-7184-769c-873c-ac94545331be" xlink:to="loc_us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets_019caf13-7184-7cce-a030-b0d60283e4fc" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/RegulatoryCapitalandOtherRegulatoryMattersScheduleofCommonShareRepurchasesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#RegulatoryCapitalandOtherRegulatoryMattersScheduleofCommonShareRepurchasesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/RegulatoryCapitalandOtherRegulatoryMattersScheduleofCommonShareRepurchasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcceleratedShareRepurchasesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcceleratedShareRepurchasesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019caf13-7184-717d-b486-79f4712bfef1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019caf13-7184-717d-b486-79f4712bfef1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-7184-717d-b486-79f4712bfef1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-7184-717d-b486-79f4712bfef1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-7184-717d-b486-79f4712bfef1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019caf13-7184-73f9-bcc1-d6725e72726f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019caf13-7184-717d-b486-79f4712bfef1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019caf13-7184-73f9-bcc1-d6725e72726f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019caf13-7184-712d-83ac-6cf3905cb36c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019caf13-7184-73f9-bcc1-d6725e72726f" xlink:to="loc_us-gaap_UnsecuredDebtMember_019caf13-7184-712d-83ac-6cf3905cb36c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019caf13-7184-75c2-86e4-66cf24cd1a83" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_dei_LegalEntityAxis_019caf13-7184-75c2-86e4-66cf24cd1a83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019caf13-7184-75c2-86e4-66cf24cd1a83_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019caf13-7184-75c2-86e4-66cf24cd1a83" xlink:to="loc_dei_EntityDomain_019caf13-7184-75c2-86e4-66cf24cd1a83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019caf13-7184-7c5e-a603-f40dcc678dfd" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019caf13-7184-75c2-86e4-66cf24cd1a83" xlink:to="loc_dei_EntityDomain_019caf13-7184-7c5e-a603-f40dcc678dfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AllyFinancialIncMember_019caf13-7184-7911-a146-cc3f79165a72" xlink:href="ally-20260331.xsd#ally_AllyFinancialIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019caf13-7184-7c5e-a603-f40dcc678dfd" xlink:to="loc_ally_AllyFinancialIncMember_019caf13-7184-7911-a146-cc3f79165a72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7b71-947c-89a8666089b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7b71-947c-89a8666089b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7b71-947c-89a8666089b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7b71-947c-89a8666089b5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7b71-947c-89a8666089b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-758e-9464-e4f8272f2510" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7b71-947c-89a8666089b5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-758e-9464-e4f8272f2510" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019caf13-7184-7e33-9f57-27c4c7e07eb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-758e-9464-e4f8272f2510" xlink:to="loc_us-gaap_AutomobileLoanMember_019caf13-7184-7e33-9f57-27c4c7e07eb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019caf13-7184-7a58-b4b6-c7478b602dcf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_us-gaap_DebtInstrumentAxis_019caf13-7184-7a58-b4b6-c7478b602dcf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7184-7a58-b4b6-c7478b602dcf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-7184-7a58-b4b6-c7478b602dcf" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7184-7a58-b4b6-c7478b602dcf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7184-741e-92a0-2f7bc6d5c94b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019caf13-7184-7a58-b4b6-c7478b602dcf" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7184-741e-92a0-2f7bc6d5c94b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CreditLinkedNotesMember_019caf13-7184-7e56-b0e1-03f1f3afa9fc" xlink:href="ally-20260331.xsd#ally_CreditLinkedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019caf13-7184-741e-92a0-2f7bc6d5c94b" xlink:to="loc_ally_CreditLinkedNotesMember_019caf13-7184-7e56-b0e1-03f1f3afa9fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-761f-b0ee-0beb8ec9c396" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-761f-b0ee-0beb8ec9c396" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-761f-b0ee-0beb8ec9c396_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-761f-b0ee-0beb8ec9c396" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-761f-b0ee-0beb8ec9c396_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7df5-a147-d1034e2edba1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-761f-b0ee-0beb8ec9c396" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7df5-a147-d1034e2edba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-7184-74a2-ace0-7ce37fc07a88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7df5-a147-d1034e2edba1" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019caf13-7184-74a2-ace0-7ce37fc07a88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019d41fd-1082-789c-8055-ea5dad96f193" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesTable_019caf13-7184-7d0e-9298-1a1ebbc77fba" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019d41fd-1082-789c-8055-ea5dad96f193" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d41fd-1082-789c-8055-ea5dad96f193_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d41fd-1082-789c-8055-ea5dad96f193" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d41fd-1082-789c-8055-ea5dad96f193_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d41fd-1082-72ee-93a0-f0f301ba51c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d41fd-1082-789c-8055-ea5dad96f193" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d41fd-1082-72ee-93a0-f0f301ba51c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019d41fd-5070-7123-a2fd-c522c2b343bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019d41fd-1082-72ee-93a0-f0f301ba51c5" xlink:to="loc_us-gaap_SubsequentEventMember_019d41fd-5070-7123-a2fd-c522c2b343bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum_019caf13-7184-7137-abba-d016469d6f23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_BankingRegulationCapitalConservationBufferCapitalConservedMinimum_019caf13-7184-7137-abba-d016469d6f23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019caf13-7184-7392-8a2f-c567be085eda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019caf13-7184-7392-8a2f-c567be085eda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtInstrumentReferencePortfolioAmount_019caf13-7184-7bb9-8aba-5aae9ac33147" xlink:href="ally-20260331.xsd#ally_DebtInstrumentReferencePortfolioAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_ally_DebtInstrumentReferencePortfolioAmount_019caf13-7184-7bb9-8aba-5aae9ac33147" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtInstrumentReferenceAssetAmount_019caf13-7184-76e1-bce8-8dc47e4c5c59" xlink:href="ally-20260331.xsd#ally_DebtInstrumentReferenceAssetAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_ally_DebtInstrumentReferenceAssetAmount_019caf13-7184-76e1-bce8-8dc47e4c5c59" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019caf13-7184-7b6b-888e-46518726334e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019caf13-7184-7b6b-888e-46518726334e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019caf13-7184-7282-aebe-bcf9db3a9863" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019caf13-7184-7282-aebe-bcf9db3a9863" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019caf13-7184-726a-b1d5-17ef770566fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019caf13-7184-726a-b1d5-17ef770566fe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019caf13-7184-76df-abed-ae15192ff34f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019caf13-7184-76df-abed-ae15192ff34f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableAmountPerShare_019caf13-7184-7be5-8a9d-d0ceb13803aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsPayableAmountPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_DividendsPayableAmountPerShare_019caf13-7184-7be5-8a9d-d0ceb13803aa" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019caf13-7184-7a24-8123-a6d260a716a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcceleratedShareRepurchasesLineItems_019caf13-7184-75d5-a39a-59c0398dd77b" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019caf13-7184-7a24-8123-a6d260a716a5" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueAmountsofDerivativeInstrumentsReportedonourCondensedConsolidatedBalanceSheetDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueAmountsofDerivativeInstrumentsReportedonourCondensedConsolidatedBalanceSheetDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueAmountsofDerivativeInstrumentsReportedonourCondensedConsolidatedBalanceSheetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019caf13-7184-70f8-88b1-7b5b2d1da744" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf13-7184-712d-9f44-a92f5109b97c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf13-7184-70f8-88b1-7b5b2d1da744" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf13-7184-712d-9f44-a92f5109b97c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7583-b488-5349369fc9a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf13-7184-712d-9f44-a92f5109b97c" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7583-b488-5349369fc9a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7583-b488-5349369fc9a5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7583-b488-5349369fc9a5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7583-b488-5349369fc9a5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7583-b488-5349369fc9a5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019caf13-7184-7d17-808d-9046ce3036a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:to="loc_us-gaap_InterestRateContractMember_019caf13-7184-7d17-808d-9046ce3036a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019caf13-7184-7c0c-85cc-b6c87c1574d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestRateContractMember_019caf13-7184-7d17-808d-9046ce3036a1" xlink:to="loc_us-gaap_InterestRateSwapMember_019caf13-7184-7c0c-85cc-b6c87c1574d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestRatePurchasedOptionsMember_019caf13-7184-7985-890b-ceab7b1bab5b" xlink:href="ally-20260331.xsd#ally_InterestRatePurchasedOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestRateContractMember_019caf13-7184-7d17-808d-9046ce3036a1" xlink:to="loc_ally_InterestRatePurchasedOptionsMember_019caf13-7184-7985-890b-ceab7b1bab5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7cdc-96c1-ad90e5254dfc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7cdc-96c1-ad90e5254dfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019caf13-7184-7f47-8241-2b9fafb58555" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7cdc-96c1-ad90e5254dfc" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019caf13-7184-7f47-8241-2b9fafb58555" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditRiskContractMember_019caf13-7184-7e25-ae30-643f201d4e0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditRiskContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:to="loc_us-gaap_CreditRiskContractMember_019caf13-7184-7e25-ae30-643f201d4e0c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CreditLinkedNoteDerivativesMember_019caf13-7184-7196-a6c1-a4b6c7946a13" xlink:href="ally-20260331.xsd#ally_CreditLinkedNoteDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditRiskContractMember_019caf13-7184-7e25-ae30-643f201d4e0c" xlink:to="loc_ally_CreditLinkedNoteDerivativesMember_019caf13-7184-7196-a6c1-a4b6c7946a13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityContractMember_019d9f6a-f645-7bbe-9762-ca974133ce06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b0d-81c5-be0784d88557" xlink:to="loc_us-gaap_EquityContractMember_019d9f6a-f645-7bbe-9762-ca974133ce06" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_EquityContractWrittenOptionMember_019d9f6b-2221-7eb5-80be-7cb941f7e58a" xlink:href="ally-20260331.xsd#ally_EquityContractWrittenOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityContractMember_019d9f6a-f645-7bbe-9762-ca974133ce06" xlink:to="loc_ally_EquityContractWrittenOptionMember_019d9f6b-2221-7eb5-80be-7cb941f7e58a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7f0b-a547-294153c42d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf13-7184-712d-9f44-a92f5109b97c" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7f0b-a547-294153c42d8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7f0b-a547-294153c42d8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7f0b-a547-294153c42d8e" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7f0b-a547-294153c42d8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7932-b836-9c894e8fc586" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7f0b-a547-294153c42d8e" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7932-b836-9c894e8fc586" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7526-8d81-acd5dc226b64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7932-b836-9c894e8fc586" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7526-8d81-acd5dc226b64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019caf13-7184-7c27-8765-037937d34409" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7932-b836-9c894e8fc586" xlink:to="loc_us-gaap_NondesignatedMember_019caf13-7184-7c27-8765-037937d34409" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019caf13-7184-7c0a-9cff-bd865f4cfd48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf13-7184-70f8-88b1-7b5b2d1da744" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019caf13-7184-7c0a-9cff-bd865f4cfd48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019caf13-7184-7717-8dbc-078e22b97c46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf13-7184-70f8-88b1-7b5b2d1da744" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019caf13-7184-7717-8dbc-078e22b97c46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019caf13-7184-7547-9908-f80a95f03073" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf13-7184-70f8-88b1-7b5b2d1da744" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019caf13-7184-7547-9908-f80a95f03073" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueHedgingInstrumentsStatementsofFinancialPerformanceandFinancialPositionLocationDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueHedgingInstrumentsStatementsofFinancialPerformanceandFinancialPositionLocationDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofFairValueHedgingInstrumentsStatementsofFinancialPerformanceandFinancialPositionLocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019caf13-7184-7c44-8c7e-375c41e9c1f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019caf13-7184-7c44-8c7e-375c41e9c1f3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7c3b-b70c-1f45f25c2bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019caf13-7184-7c44-8c7e-375c41e9c1f3" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7c3b-b70c-1f45f25c2bc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7c3b-b70c-1f45f25c2bc8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7c3b-b70c-1f45f25c2bc8" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7c3b-b70c-1f45f25c2bc8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7668-b685-03ce1db34dca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7c3b-b70c-1f45f25c2bc8" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7668-b685-03ce1db34dca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DiscontinuedHedgeMember_019caf13-7184-7422-b797-8adc47de58dc" xlink:href="ally-20260331.xsd#ally_DiscontinuedHedgeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7668-b685-03ce1db34dca" xlink:to="loc_ally_DiscontinuedHedgeMember_019caf13-7184-7422-b797-8adc47de58dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019caf13-7184-75d2-ba11-8631599e66f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019caf13-7184-7c44-8c7e-375c41e9c1f3" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019caf13-7184-75d2-ba11-8631599e66f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-75d2-ba11-8631599e66f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019caf13-7184-75d2-ba11-8631599e66f1" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-75d2-ba11-8631599e66f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-7464-a28e-dd929631665e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019caf13-7184-75d2-ba11-8631599e66f1" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-7464-a28e-dd929631665e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AvailableForSaleDebtSecuritiesLocationMember_019caf13-7184-71b3-a437-298acd956133" xlink:href="ally-20260331.xsd#ally_AvailableForSaleDebtSecuritiesLocationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-7464-a28e-dd929631665e" xlink:to="loc_ally_AvailableForSaleDebtSecuritiesLocationMember_019caf13-7184-71b3-a437-298acd956133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancereceivablesandLoansnetMember_019caf13-7184-7e62-be02-b01530261663" xlink:href="ally-20260331.xsd#ally_FinancereceivablesandLoansnetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-7464-a28e-dd929631665e" xlink:to="loc_ally_FinancereceivablesandLoansnetMember_019caf13-7184-7e62-be02-b01530261663" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LongTermDebtLocationMember_019caf13-7184-7336-a3a2-44fd262a262b" xlink:href="ally-20260331.xsd#ally_LongTermDebtLocationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019caf13-7184-7464-a28e-dd929631665e" xlink:to="loc_ally_LongTermDebtLocationMember_019caf13-7184-7336-a3a2-44fd262a262b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7b74-82ee-cf1392b08340" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_019caf13-7184-7c44-8c7e-375c41e9c1f3" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7b74-82ee-cf1392b08340" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7b74-82ee-cf1392b08340_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7b74-82ee-cf1392b08340" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7b74-82ee-cf1392b08340_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7bd4-85b2-952cfb3f3adb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-7b74-82ee-cf1392b08340" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7bd4-85b2-952cfb3f3adb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7ea5-bd06-fce6d171d27b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7bd4-85b2-952cfb3f3adb" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7ea5-bd06-fce6d171d27b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedge_019caf13-7184-7ce5-98fc-be18a8a99d2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetFairValueHedge_019caf13-7184-7ce5-98fc-be18a8a99d2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7735-be52-e53c8ba6a95f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7735-be52-e53c8ba6a95f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7972-97ac-b9f1bde3bf3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7972-97ac-b9f1bde3bf3a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedge_019caf13-7184-73cb-9425-7644b44cc35f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityFairValueHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedge_019caf13-7184-73cb-9425-7644b44cc35f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7b9a-ae5a-d9c9830a3606" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7b9a-ae5a-d9c9830a3606" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityDiscontinuedFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7cbc-8f14-c8ff7f56c107" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityDiscontinuedFairValueHedgeCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedLiabilityDiscontinuedFairValueHedgeCumulativeIncreaseDecrease_019caf13-7184-7cbc-8f14-c8ff7f56c107" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetStatementOfFinancialPositionExtensibleEnumeration_019caf13-7184-797a-b49e-9284c213f910" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetStatementOfFinancialPositionExtensibleEnumeration_019caf13-7184-797a-b49e-9284c213f910" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedLiabilityStatementOfFinancialPositionExtensibleEnumeration_019caf13-7184-78d2-9b39-8b64694fb102" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedLiabilityStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedLiabilityStatementOfFinancialPositionExtensibleEnumeration_019caf13-7184-78d2-9b39-8b64694fb102" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClosedPortfolioAndBeneficialInterestLastOfLayerAmortizedCost_019caf13-7184-78b5-9aef-3dcb23264311" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClosedPortfolioAndBeneficialInterestLastOfLayerAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_ClosedPortfolioAndBeneficialInterestLastOfLayerAmortizedCost_019caf13-7184-78b5-9aef-3dcb23264311" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost_019caf13-7184-76e3-89dd-361d0c21cf01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost_019caf13-7184-76e3-89dd-361d0c21cf01" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease_019caf13-7184-7c66-aeae-f19cae7b59cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease_019caf13-7184-7c66-aeae-f19cae7b59cf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgedAssetFairValueHedgeLastOfLayerAmount_019caf13-7184-7e2b-801a-cc32bd3e35ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgedAssetFairValueHedgeLastOfLayerAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_us-gaap_HedgedAssetFairValueHedgeLastOfLayerAmount_019caf13-7184-7e2b-801a-cc32bd3e35ea" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_ClosedPortfolioLastOfLayerCarryingValue_019caf13-7184-77b9-ba1a-473be9084c34" xlink:href="ally-20260331.xsd#ally_ClosedPortfolioLastOfLayerCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_019caf13-7184-77dd-9d2b-9821afe6145c" xlink:to="loc_ally_ClosedPortfolioLastOfLayerCarryingValue_019caf13-7184-77b9-ba1a-473be9084c34" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofStatementofGainsandLossesonDerivativeInstrumentsReportedinStatementofComprehensiveIncomeDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofStatementofGainsandLossesonDerivativeInstrumentsReportedinStatementofComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofStatementofGainsandLossesonDerivativeInstrumentsReportedinStatementofComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7cc6-97db-a32799d96d47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7864-a67f-15a2dc43be47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7cc6-97db-a32799d96d47" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7864-a67f-15a2dc43be47" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7b46-a45e-bad197cd59f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7864-a67f-15a2dc43be47" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7b46-a45e-bad197cd59f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7b46-a45e-bad197cd59f8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7b46-a45e-bad197cd59f8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7b46-a45e-bad197cd59f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-79a6-a00d-a374e485b4ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7b46-a45e-bad197cd59f8" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-79a6-a00d-a374e485b4ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_GainLossOnMortgageAndAutomotiveLoansMember_019caf13-7184-7f36-8080-47d283b820d0" xlink:href="ally-20260331.xsd#ally_GainLossOnMortgageAndAutomotiveLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-79a6-a00d-a374e485b4ac" xlink:to="loc_ally_GainLossOnMortgageAndAutomotiveLoansMember_019caf13-7184-7f36-8080-47d283b820d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseMember_019caf13-7184-703d-91ec-eb845ffdb357" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherOperatingIncomeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-79a6-a00d-a374e485b4ac" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseMember_019caf13-7184-703d-91ec-eb845ffdb357" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeMember_019caf13-7184-7c95-8fde-35a817c5ffe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-79a6-a00d-a374e485b4ac" xlink:to="loc_us-gaap_OtherIncomeMember_019caf13-7184-7c95-8fde-35a817c5ffe4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-71cc-b56a-741361476832" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7864-a67f-15a2dc43be47" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-71cc-b56a-741361476832" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-71cc-b56a-741361476832_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-71cc-b56a-741361476832" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-71cc-b56a-741361476832_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b06-99e2-d7f37c16f01f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-71cc-b56a-741361476832" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b06-99e2-d7f37c16f01f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019caf13-7184-71b5-9ab2-1dcf7cd0e76a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b06-99e2-d7f37c16f01f" xlink:to="loc_us-gaap_InterestRateContractMember_019caf13-7184-71b5-9ab2-1dcf7cd0e76a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-72e0-b245-293472aff180" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b06-99e2-d7f37c16f01f" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-72e0-b245-293472aff180" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCreditDerivativesMember_019caf13-7184-7994-9b35-db2ad071e149" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCreditDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7b06-99e2-d7f37c16f01f" xlink:to="loc_us-gaap_OtherCreditDerivativesMember_019caf13-7184-7994-9b35-db2ad071e149" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-71dd-9450-783a31138037" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7864-a67f-15a2dc43be47" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-71dd-9450-783a31138037" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-71dd-9450-783a31138037_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-71dd-9450-783a31138037" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-71dd-9450-783a31138037_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-725f-bd01-2bed37179712" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-71dd-9450-783a31138037" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-725f-bd01-2bed37179712" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019caf13-7184-7ddf-b026-dd36f36bb1c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-725f-bd01-2bed37179712" xlink:to="loc_us-gaap_NondesignatedMember_019caf13-7184-7ddf-b026-dd36f36bb1c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019caf13-7184-7dc9-b5c0-82b682f1b943" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7cc6-97db-a32799d96d47" xlink:to="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019caf13-7184-7dc9-b5c0-82b682f1b943" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsDesignatedasFairValueHedgesGainLossDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsDesignatedasFairValueHedgesGainLossDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsDesignatedasFairValueHedgesGainLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-70e3-a6cc-876d2a366580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-70e3-a6cc-876d2a366580" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-75be-a360-a73b86730184" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-70e3-a6cc-876d2a366580" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-75be-a360-a73b86730184" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-75be-a360-a73b86730184_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-75be-a360-a73b86730184" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-75be-a360-a73b86730184_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7ba2-9580-012ed7e5dfed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-75be-a360-a73b86730184" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7ba2-9580-012ed7e5dfed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7bd6-af1c-9a9d61707874" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-7ba2-9580-012ed7e5dfed" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7bd6-af1c-9a9d61707874" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-710b-a564-46c1c6fba2b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-70e3-a6cc-876d2a366580" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-710b-a564-46c1c6fba2b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-710b-a564-46c1c6fba2b0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-710b-a564-46c1c6fba2b0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-710b-a564-46c1c6fba2b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-729d-a70a-74d21c3fe6e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-710b-a564-46c1c6fba2b0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-729d-a70a-74d21c3fe6e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-703e-a88f-935caf5074ee" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesAvailableForSaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-729d-a70a-74d21c3fe6e8" xlink:to="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-703e-a88f-935caf5074ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FixedrateAutomotiveLoansMember_019caf13-7184-78bc-a51f-2ef219ef3ceb" xlink:href="ally-20260331.xsd#ally_FixedrateAutomotiveLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-729d-a70a-74d21c3fe6e8" xlink:to="loc_ally_FixedrateAutomotiveLoansMember_019caf13-7184-78bc-a51f-2ef219ef3ceb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_VariableRateCommercialBorrowingsMember_019d012d-a362-7a67-9789-2947b35d209c" xlink:href="ally-20260331.xsd#ally_VariableRateCommercialBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-729d-a70a-74d21c3fe6e8" xlink:to="loc_ally_VariableRateCommercialBorrowingsMember_019d012d-a362-7a67-9789-2947b35d209c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7740-872d-279ceb8dba9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-70e3-a6cc-876d2a366580" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7740-872d-279ceb8dba9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7740-872d-279ceb8dba9c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7740-872d-279ceb8dba9c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7740-872d-279ceb8dba9c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7109-bd2f-3434fc6e5ea5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7740-872d-279ceb8dba9c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7109-bd2f-3434fc6e5ea5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestAndFeesOnFinanceReceivablesAndLoansMember_019caf13-7184-7b7d-be83-8d1ad1828c13" xlink:href="ally-20260331.xsd#ally_InterestAndFeesOnFinanceReceivablesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7109-bd2f-3434fc6e5ea5" xlink:to="loc_ally_InterestAndFeesOnFinanceReceivablesAndLoansMember_019caf13-7184-7b7d-be83-8d1ad1828c13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember_019caf13-7184-771a-9523-879215182395" xlink:href="ally-20260331.xsd#ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7109-bd2f-3434fc6e5ea5" xlink:to="loc_ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember_019caf13-7184-771a-9523-879215182395" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestOnLongTermDebtMember_019caf13-7184-7129-b7a9-9189c2c1fb3c" xlink:href="ally-20260331.xsd#ally_InterestOnLongTermDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7109-bd2f-3434fc6e5ea5" xlink:to="loc_ally_InterestOnLongTermDebtMember_019caf13-7184-7129-b7a9-9189c2c1fb3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1_019caf13-7184-7033-84d1-95fb63f0eb19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1_019caf13-7184-7033-84d1-95fb63f0eb19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_019caf13-7184-7cd8-94a3-d5311b25ebb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_019caf13-7184-7cd8-94a3-d5311b25ebb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_019caf13-7184-75be-99be-9ba728f979c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_019caf13-7184-75be-99be-9ba728f979c3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_019caf13-7184-77cc-9224-b856d15ce21d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_019caf13-7184-77cc-9224-b856d15ce21d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019caf13-7184-7629-aa8e-090d7d18e1ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019caf13-7184-7629-aa8e-090d7d18e1ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndFeeIncomeLoansAndLeasesHeldInPortfolio_019caf13-7184-76a3-8106-93459ed59ded" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestAndFeeIncomeLoansAndLeasesHeldInPortfolio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_InterestAndFeeIncomeLoansAndLeasesHeldInPortfolio_019caf13-7184-76a3-8106-93459ed59ded" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestAndDividendIncomeSecuritiesAndOtherEarningAssetsOperating_019caf13-7184-740b-9de0-701f6bac213e" xlink:href="ally-20260331.xsd#ally_InterestAndDividendIncomeSecuritiesAndOtherEarningAssetsOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_ally_InterestAndDividendIncomeSecuritiesAndOtherEarningAssetsOperating_019caf13-7184-740b-9de0-701f6bac213e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseLongTermDebt_019caf13-7184-7b59-8caa-f0e445875054" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_InterestExpenseLongTermDebt_019caf13-7184-7b59-8caa-f0e445875054" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths_019caf13-7184-7093-a29f-6c5b8a3e2dfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7834-8e05-d6d251177496" xlink:to="loc_us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths_019caf13-7184-7093-a29f-6c5b8a3e2dfb" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofInterestandAmortizationonDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofInterestandAmortizationonDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofInterestandAmortizationonDerivativeInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7e95-9acc-d4e6acdd475b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7641-9aeb-6ec6ea544ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7e95-9acc-d4e6acdd475b" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7641-9aeb-6ec6ea544ae7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-775e-a747-8751e40e9f4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7641-9aeb-6ec6ea544ae7" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-775e-a747-8751e40e9f4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-775e-a747-8751e40e9f4d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-775e-a747-8751e40e9f4d" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-775e-a747-8751e40e9f4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-75e0-b362-f571e8cbf7fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf13-7184-775e-a747-8751e40e9f4d" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-75e0-b362-f571e8cbf7fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7599-a6c7-f0dfc89ae50e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf13-7184-75e0-b362-f571e8cbf7fc" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019caf13-7184-7599-a6c7-f0dfc89ae50e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-7010-9bcf-1e6cafa7f2b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7641-9aeb-6ec6ea544ae7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-7010-9bcf-1e6cafa7f2b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7010-9bcf-1e6cafa7f2b6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-7010-9bcf-1e6cafa7f2b6" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7010-9bcf-1e6cafa7f2b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7305-aceb-10b4c5dc48e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019caf13-7184-7010-9bcf-1e6cafa7f2b6" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7305-aceb-10b4c5dc48e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019caf13-7184-710e-8ac0-7522e5115b53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7305-aceb-10b4c5dc48e3" xlink:to="loc_us-gaap_UnsecuredDebtMember_019caf13-7184-710e-8ac0-7522e5115b53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-7433-a52a-48655e149bd0" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesAvailableForSaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7305-aceb-10b4c5dc48e3" xlink:to="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-7433-a52a-48655e149bd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FixedrateAutomotiveLoansMember_019caf13-7184-7a98-9eb9-c2baa207c507" xlink:href="ally-20260331.xsd#ally_FixedrateAutomotiveLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019caf13-7184-7305-aceb-10b4c5dc48e3" xlink:to="loc_ally_FixedrateAutomotiveLoansMember_019caf13-7184-7a98-9eb9-c2baa207c507" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7fda-9af6-8fb0adad9abd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7641-9aeb-6ec6ea544ae7" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7fda-9af6-8fb0adad9abd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7fda-9af6-8fb0adad9abd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7fda-9af6-8fb0adad9abd" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7fda-9af6-8fb0adad9abd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7db7-9854-43dfcbf57373" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019caf13-7184-7fda-9af6-8fb0adad9abd" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7db7-9854-43dfcbf57373" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestAndFeesOnFinanceReceivablesAndLoansMember_019caf13-7184-7eb1-bb35-5acc1d501de3" xlink:href="ally-20260331.xsd#ally_InterestAndFeesOnFinanceReceivablesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7db7-9854-43dfcbf57373" xlink:to="loc_ally_InterestAndFeesOnFinanceReceivablesAndLoansMember_019caf13-7184-7eb1-bb35-5acc1d501de3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember_019caf13-7184-78a0-9107-25a3f9e1a56b" xlink:href="ally-20260331.xsd#ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7db7-9854-43dfcbf57373" xlink:to="loc_ally_InterestAndDividendsOnInvestmentSecuritiesAndOtherEarningAssetsMember_019caf13-7184-78a0-9107-25a3f9e1a56b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InterestOnLongTermDebtMember_019caf13-7184-7f46-a891-e2f509967690" xlink:href="ally-20260331.xsd#ally_InterestOnLongTermDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019caf13-7184-7db7-9854-43dfcbf57373" xlink:to="loc_ally_InterestOnLongTermDebtMember_019caf13-7184-7f46-a891-e2f509967690" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_GainLossOnAmortizationOfDeferredBasisAdjustments_019caf13-7184-711f-af41-093d5c88905b" xlink:href="ally-20260331.xsd#ally_GainLossOnAmortizationOfDeferredBasisAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7e95-9acc-d4e6acdd475b" xlink:to="loc_ally_GainLossOnAmortizationOfDeferredBasisAdjustments_019caf13-7184-711f-af41-093d5c88905b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_GainLossOnInterestForQualifyingHedge_019caf13-7184-7821-ad63-a68970e1f39a" xlink:href="ally-20260331.xsd#ally_GainLossOnInterestForQualifyingHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7e95-9acc-d4e6acdd475b" xlink:to="loc_ally_GainLossOnInterestForQualifyingHedge_019caf13-7184-7821-ad63-a68970e1f39a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_TotalInterestAndAmortizationIncomeExpenseHedgingRelationship_019caf13-7184-7618-827d-7cc9daa1a568" xlink:href="ally-20260331.xsd#ally_TotalInterestAndAmortizationIncomeExpenseHedgingRelationship"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7e95-9acc-d4e6acdd475b" xlink:to="loc_ally_TotalInterestAndAmortizationIncomeExpenseHedgingRelationship_019caf13-7184-7618-827d-7cc9daa1a568" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsUsedinNetInvestmentHedgeAccountingRelationshipsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsUsedinNetInvestmentHedgeAccountingRelationshipsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/DerivativeInstrumentsandHedgingActivitiesScheduleofDerivativeInstrumentsUsedinNetInvestmentHedgeAccountingRelationshipsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7beb-8e75-515e0d960015" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7beb-8e75-515e0d960015" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7341-bb53-34bc0d2d880f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7beb-8e75-515e0d960015" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7341-bb53-34bc0d2d880f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7341-bb53-34bc0d2d880f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7341-bb53-34bc0d2d880f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-7341-bb53-34bc0d2d880f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-79d3-8ddd-091d2e36bb60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf13-7184-7341-bb53-34bc0d2d880f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-79d3-8ddd-091d2e36bb60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019caf13-7184-77ed-8d3d-50d000bc5b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-79d3-8ddd-091d2e36bb60" xlink:to="loc_us-gaap_InterestRateContractMember_019caf13-7184-77ed-8d3d-50d000bc5b3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-772a-9f3a-f87851b3e568" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf13-7184-79d3-8ddd-091d2e36bb60" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-772a-9f3a-f87851b3e568" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7f84-a00f-6edaa6917510" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019caf13-7184-7beb-8e75-515e0d960015" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7f84-a00f-6edaa6917510" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7f84-a00f-6edaa6917510_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7f84-a00f-6edaa6917510" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7f84-a00f-6edaa6917510_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7236-b892-b2798f9f57b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019caf13-7184-7f84-a00f-6edaa6917510" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7236-b892-b2798f9f57b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_019caf13-7184-71d7-8c50-45ae7a56c372" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7236-b892-b2798f9f57b1" xlink:to="loc_us-gaap_CashFlowHedgingMember_019caf13-7184-71d7-8c50-45ae7a56c372" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_019caf13-7184-76cc-b4c0-9a16c7fbd649" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019caf13-7184-7236-b892-b2798f9f57b1" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_019caf13-7184-76cc-b4c0-9a16c7fbd649" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019caf13-7184-74ef-b832-f2a49cec0583" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019caf13-7184-74ef-b832-f2a49cec0583" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax_019caf13-7184-74d0-99ec-681e99d48622" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax_019caf13-7184-74d0-99ec-681e99d48622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeExcludedComponentGainLossRecognizedInEarnings_019caf13-7184-7d30-9a37-b13cc06245bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeExcludedComponentGainLossRecognizedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:to="loc_us-gaap_DerivativeExcludedComponentGainLossRecognizedInEarnings_019caf13-7184-7d30-9a37-b13cc06245bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax_019caf13-7184-73de-b6af-16ebf186f849" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019caf13-7184-7a77-a26b-23897c53a04c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax_019caf13-7184-73de-b6af-16ebf186f849" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsRecurringBasisDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FairValueScheduleofFairValueMeasurementsRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-70d2-b1d9-0eb73ce6a5ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-70d2-b1d9-0eb73ce6a5ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-70d2-b1d9-0eb73ce6a5ec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-70d2-b1d9-0eb73ce6a5ec" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-70d2-b1d9-0eb73ce6a5ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-72d9-aff4-acb5801a7be1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-70d2-b1d9-0eb73ce6a5ec" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-72d9-aff4-acb5801a7be1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019caf13-7184-71b7-a3a6-1d7ae1eb05d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-72d9-aff4-acb5801a7be1" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019caf13-7184-71b7-a3a6-1d7ae1eb05d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-709a-8a5c-b91d69340cd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-709a-8a5c-b91d69340cd1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-709a-8a5c-b91d69340cd1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-709a-8a5c-b91d69340cd1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-709a-8a5c-b91d69340cd1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d9f-9999-66fc18fd3ec8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-709a-8a5c-b91d69340cd1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d9f-9999-66fc18fd3ec8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-7ef4-ba9b-f2d26a174e26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d9f-9999-66fc18fd3ec8" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-7ef4-ba9b-f2d26a174e26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-7f4c-8f65-16285cb7e76a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d9f-9999-66fc18fd3ec8" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-7f4c-8f65-16285cb7e76a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7bbf-8095-7c279cf55066" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d9f-9999-66fc18fd3ec8" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7bbf-8095-7c279cf55066" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7713-be3d-f9cecbf3b327" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7713-be3d-f9cecbf3b327" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7713-be3d-f9cecbf3b327_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7713-be3d-f9cecbf3b327" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7713-be3d-f9cecbf3b327_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7713-be3d-f9cecbf3b327" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_019caf13-7184-7c70-9874-79c0c3295180" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_EquitySecuritiesMember_019caf13-7184-7c70-9874-79c0c3295180" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7184-732b-94ff-87283c3de76e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019caf13-7184-732b-94ff-87283c3de76e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7184-70f4-8bc4-03a576bab4c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019caf13-7184-70f4-8bc4-03a576bab4c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7184-7c78-ad45-8fdd34e81506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019caf13-7184-7c78-ad45-8fdd34e81506" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7184-7a7a-8b30-5e9ca2d05bbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_019caf13-7184-7a7a-8b30-5e9ca2d05bbc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7184-7d30-8f01-1f5049a20e90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019caf13-7184-7d30-8f01-1f5049a20e90" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7184-76ae-8e16-d6a2820d817a" xlink:href="ally-20260331.xsd#ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_ally_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesCommercialMember_019caf13-7184-76ae-8e16-d6a2820d817a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7184-7645-b5fe-1e38f9995257" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_019caf13-7184-7645-b5fe-1e38f9995257" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7184-76b9-8ad4-8b8edc0f4016" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019caf13-7184-76b9-8ad4-8b8edc0f4016" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019d9f7e-f0dc-743d-9d1f-33facb5a4465" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_InterestRateContractMember_019d9f7e-f0dc-743d-9d1f-33facb5a4465" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7b63-bf0c-5fffe6cf5159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-762b-86a0-e6e947fc1660" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7b63-bf0c-5fffe6cf5159" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-7e48-8fee-f677a0a163a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-7f07-952f-ab6274b078ad" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-7e48-8fee-f677a0a163a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7e48-8fee-f677a0a163a2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-7e48-8fee-f677a0a163a2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7e48-8fee-f677a0a163a2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-7e48-8fee-f677a0a163a2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019d9f7e-f0dc-7882-bb70-e2d870961aed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:to="loc_us-gaap_InterestRateContractMember_019d9f7e-f0dc-7882-bb70-e2d870961aed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7d99-a9fa-4861b19ffd7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf13-7184-7d99-a9fa-4861b19ffd7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCreditDerivativesMember_019d9f7e-f0dc-762f-9205-4881c35e77ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCreditDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:to="loc_us-gaap_OtherCreditDerivativesMember_019d9f7e-f0dc-762f-9205-4881c35e77ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityContractMember_019d9f7e-f0dc-7fbe-ae04-6aa1372d3c1d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7aa6-9b16-68d7c50c585f" xlink:to="loc_us-gaap_EquityContractMember_019d9f7e-f0dc-7fbe-ae04-6aa1372d3c1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019caf13-7184-7b27-89af-e23925240b00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_019caf13-7184-7b27-89af-e23925240b00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7184-7863-8217-aa8804a63779" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019caf13-7184-7863-8217-aa8804a63779" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration_019d9f7e-f0dc-7abe-9b52-37278837071f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:to="loc_us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration_019d9f7e-f0dc-7abe-9b52-37278837071f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019d9f7e-f0dc-7748-87d4-bb484b613455" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:to="loc_us-gaap_DerivativeAssets_019d9f7e-f0dc-7748-87d4-bb484b613455" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019caf13-7184-77a6-b98c-c3ddf133af41" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf13-7184-7c77-bf73-f5ab544e0c57" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019caf13-7184-77a6-b98c-c3ddf133af41" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf13-7184-799d-bfe3-2204efa6f234" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf13-7184-799d-bfe3-2204efa6f234" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019caf13-7184-78fd-b7e4-9bddac6a02c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf13-7184-799d-bfe3-2204efa6f234" xlink:to="loc_us-gaap_DerivativeLiabilities_019caf13-7184-78fd-b7e4-9bddac6a02c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019caf13-7184-7304-b7d4-4714928710ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf13-7184-799d-bfe3-2204efa6f234" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019caf13-7184-7304-b7d4-4714928710ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_EquityInvestmentInAnyOneIndustryDidNotExceedPercentage_019caf13-7184-7a2c-b17e-2648dca79679" xlink:href="ally-20260331.xsd#ally_EquityInvestmentInAnyOneIndustryDidNotExceedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:to="loc_ally_EquityInvestmentInAnyOneIndustryDidNotExceedPercentage_019caf13-7184-7a2c-b17e-2648dca79679" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019caf13-7184-7f7f-961c-50390bf8cc0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-73f2-8f35-381417c247cd" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019caf13-7184-7f7f-961c-50390bf8cc0c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsReconciliationofLevel3AssetsAndLiabilitiesDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FairValueScheduleofFairValueMeasurementsReconciliationofLevel3AssetsAndLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsReconciliationofLevel3AssetsAndLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019caf13-7184-7dba-9401-411f7c1c0ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_019caf13-7184-74dc-a7ce-165a0455ce8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019caf13-7184-7dba-9401-411f7c1c0ec9" xlink:to="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_019caf13-7184-74dc-a7ce-165a0455ce8d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-77ce-904d-2bf1dc780ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_019caf13-7184-74dc-a7ce-165a0455ce8d" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-77ce-904d-2bf1dc780ad2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-77ce-904d-2bf1dc780ad2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-77ce-904d-2bf1dc780ad2" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-77ce-904d-2bf1dc780ad2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-77e5-8f72-27a2f56dae5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-77ce-904d-2bf1dc780ad2" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-77e5-8f72-27a2f56dae5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019caf13-7184-778e-a79d-9f2a54a4be4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-77e5-8f72-27a2f56dae5c" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019caf13-7184-778e-a79d-9f2a54a4be4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7c2f-b794-9b8790d724ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_019caf13-7184-74dc-a7ce-165a0455ce8d" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7c2f-b794-9b8790d724ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7c2f-b794-9b8790d724ec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7c2f-b794-9b8790d724ec" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7c2f-b794-9b8790d724ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7d09-b9f1-2f48e017d35a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-7c2f-b794-9b8790d724ec" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7d09-b9f1-2f48e017d35a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-75e9-88bd-e1a6e1a6c2d7" xlink:href="ally-20260331.xsd#ally_DebtSecuritiesAvailableForSaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7d09-b9f1-2f48e017d35a" xlink:to="loc_ally_DebtSecuritiesAvailableForSaleMember_019caf13-7184-75e9-88bd-e1a6e1a6c2d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LoansHeldForSaleMember_019caf13-7184-77cd-9dac-f9a3b308ea60" xlink:href="ally-20260331.xsd#ally_LoansHeldForSaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-7d09-b9f1-2f48e017d35a" xlink:to="loc_ally_LoansHeldForSaleMember_019caf13-7184-77cd-9dac-f9a3b308ea60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-703c-b126-5bc40c1ab7c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueMeasuredOnRecurringBasisGainLossIncludedInEarningsTable_019caf13-7184-74dc-a7ce-165a0455ce8d" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-703c-b126-5bc40c1ab7c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-703c-b126-5bc40c1ab7c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-703c-b126-5bc40c1ab7c2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-703c-b126-5bc40c1ab7c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7a0d-9fc5-eec0ef9993cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_019caf13-7184-703c-b126-5bc40c1ab7c2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7a0d-9fc5-eec0ef9993cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_019caf13-7184-736b-aadf-b57d496ceb99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_019caf13-7184-7a0d-9fc5-eec0ef9993cb" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_019caf13-7184-736b-aadf-b57d496ceb99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019caf13-7184-7dba-9401-411f7c1c0ec9" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019caf13-7184-7bb0-b495-2497745d2db4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019caf13-7184-7bb0-b495-2497745d2db4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_019caf13-7184-7a7b-85c7-b07b0c8318a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_019caf13-7184-7a7b-85c7-b07b0c8318a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019caf13-7184-7e82-b29a-3d3622fc2a14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_019caf13-7184-7a7b-85c7-b07b0c8318a6" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019caf13-7184-7e82-b29a-3d3622fc2a14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019caf13-7184-7ad4-b242-a52c9ae2edb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsAbstract_019caf13-7184-7a7b-85c7-b07b0c8318a6" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_019caf13-7184-7ad4-b242-a52c9ae2edb8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019caf13-7184-7924-ba3a-054ba7f52e75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019caf13-7184-7924-ba3a-054ba7f52e75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019caf13-7184-7683-9d43-37eb3d1e4cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_019caf13-7184-7683-9d43-37eb3d1e4cd9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_019caf13-7184-7696-a323-9cc6c9fe893f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_019caf13-7184-7696-a323-9cc6c9fe893f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019caf13-7184-7e01-ab98-b5d1a51f3e0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019caf13-7184-7e01-ab98-b5d1a51f3e0a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019caf13-7184-776d-ac78-2c163e2e7d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_019caf13-7184-776d-ac78-2c163e2e7d6d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_019caf13-7184-7d2c-b526-02281915be52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_019caf13-7184-7d2c-b526-02281915be52" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019caf13-7184-7e41-a6ce-5b843c53193f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FairValueAssetRecurringBasisStillHeldAbstract_019caf13-7184-77c0-ad0b-f3fe0d3931e6" xlink:href="ally-20260331.xsd#ally_FairValueAssetRecurringBasisStillHeldAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-7e73-94db-cd798cc6bab7" xlink:to="loc_ally_FairValueAssetRecurringBasisStillHeldAbstract_019caf13-7184-77c0-ad0b-f3fe0d3931e6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019caf13-7184-7d99-8ca9-ec0cde3f4dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_FairValueAssetRecurringBasisStillHeldAbstract_019caf13-7184-77c0-ad0b-f3fe0d3931e6" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019caf13-7184-7d99-8ca9-ec0cde3f4dbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossOci_019caf13-7184-7151-a3b0-d0c1437b9318" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossOci"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_FairValueAssetRecurringBasisStillHeldAbstract_019caf13-7184-77c0-ad0b-f3fe0d3931e6" xlink:to="loc_us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossOci_019caf13-7184-7151-a3b0-d0c1437b9318" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019caf13-7184-7dba-9401-411f7c1c0ec9" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019caf13-7184-7c43-8903-65b587813743" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019caf13-7184-7c43-8903-65b587813743" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossOciAbstract_019caf13-7184-78f4-9781-dd911cf59c79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossOciAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossOciAbstract_019caf13-7184-78f4-9781-dd911cf59c79" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019caf13-7184-7220-9bc5-cde3d0a7e1cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossOciAbstract_019caf13-7184-78f4-9781-dd911cf59c79" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019caf13-7184-7220-9bc5-cde3d0a7e1cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_019caf13-7184-7bfa-9d06-89ebe55acc2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetLiabilityGainLossOciAbstract_019caf13-7184-78f4-9781-dd911cf59c79" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_019caf13-7184-7bfa-9d06-89ebe55acc2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_019caf13-7184-70ca-9cfc-d0cd746e447f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_019caf13-7184-70ca-9cfc-d0cd746e447f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySales_019caf13-7184-7235-8a88-b890903b0c1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySales_019caf13-7184-7235-8a88-b890903b0c1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_019caf13-7184-792d-88cf-7de92621d42c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_019caf13-7184-792d-88cf-7de92621d42c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019caf13-7184-7dcc-9fc1-ca9eee45cae4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019caf13-7184-7dcc-9fc1-ca9eee45cae4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3_019caf13-7184-7de5-9bbd-2ce1d9b655a7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3_019caf13-7184-7de5-9bbd-2ce1d9b655a7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_019caf13-7184-7752-b44f-d196e97bd0ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019caf13-7184-74d8-9fc5-7f3db3916a5e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_019caf13-7184-7752-b44f-d196e97bd0ea" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019caf13-7184-7397-865a-6859bc7456be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FairValueLiabilityRecurringBasisStillHeldAbstract_019caf13-7184-7f95-bed7-458408257da2" xlink:href="ally-20260331.xsd#ally_FairValueLiabilityRecurringBasisStillHeldAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019caf13-7184-7dba-9401-411f7c1c0ec9" xlink:to="loc_ally_FairValueLiabilityRecurringBasisStillHeldAbstract_019caf13-7184-7f95-bed7-458408257da2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019caf13-7184-78da-b589-f8ee5580d6de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_FairValueLiabilityRecurringBasisStillHeldAbstract_019caf13-7184-7f95-bed7-458408257da2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019caf13-7184-78da-b589-f8ee5580d6de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019caf13-7184-7d4c-ae50-32ee8fe8a72f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_FairValueLiabilityRecurringBasisStillHeldAbstract_019caf13-7184-7f95-bed7-458408257da2" xlink:to="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019caf13-7184-7d4c-ae50-32ee8fe8a72f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsNonrecurringBasisDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FairValueScheduleofFairValueMeasurementsNonrecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FairValueScheduleofFairValueMeasurementsNonrecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7572-8984-1e8a57a6c8d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7572-8984-1e8a57a6c8d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7572-8984-1e8a57a6c8d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7572-8984-1e8a57a6c8d6" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7572-8984-1e8a57a6c8d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7a33-a607-98f8a97b2267" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019caf13-7184-7572-8984-1e8a57a6c8d6" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7a33-a607-98f8a97b2267" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherLoansMember_019caf13-7184-7293-ac2a-1f471c332c32" xlink:href="ally-20260331.xsd#ally_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019caf13-7184-7a33-a607-98f8a97b2267" xlink:to="loc_ally_OtherLoansMember_019caf13-7184-7293-ac2a-1f471c332c32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-7531-9f86-fbc16be90a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-7531-9f86-fbc16be90a1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7531-9f86-fbc16be90a1b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-7531-9f86-fbc16be90a1b" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7531-9f86-fbc16be90a1b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7c56-9b33-3aa10765df0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019caf13-7184-7531-9f86-fbc16be90a1b" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7c56-9b33-3aa10765df0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-7184-7ce5-8936-5c3565a4f5af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019caf13-7184-7c56-9b33-3aa10765df0b" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019caf13-7184-7ce5-8936-5c3565a4f5af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-7d82-aa6c-1bfdaa0e0b53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-7d82-aa6c-1bfdaa0e0b53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d82-aa6c-1bfdaa0e0b53_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-7d82-aa6c-1bfdaa0e0b53" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7d82-aa6c-1bfdaa0e0b53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7a56-b707-64a7338a89ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-7d82-aa6c-1bfdaa0e0b53" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7a56-b707-64a7338a89ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-7a18-8f79-28917fefcb03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7a56-b707-64a7338a89ce" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-7a18-8f79-28917fefcb03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-7d50-909b-0e7e6b874078" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7a56-b707-64a7338a89ce" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-7d50-909b-0e7e6b874078" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7a26-b53b-a1f8f7e5c4e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7a56-b707-64a7338a89ce" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7a26-b53b-a1f8f7e5c4e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-705d-abad-60bce935bb0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-705d-abad-60bce935bb0d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-705d-abad-60bce935bb0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-705d-abad-60bce935bb0d" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-705d-abad-60bce935bb0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-768a-bed4-4daa6edf5bd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019caf13-7184-705d-abad-60bce935bb0d" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-768a-bed4-4daa6edf5bd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsTotalMember_019caf13-7184-7f2a-8cf8-bb36bb02336c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019caf13-7184-768a-bed4-4daa6edf5bd9" xlink:to="loc_us-gaap_AssetsTotalMember_019caf13-7184-7f2a-8cf8-bb36bb02336c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_NonmarketableEquityInvestmentsMember_019caf13-7184-769a-93df-8874daf32946" xlink:href="ally-20260331.xsd#ally_NonmarketableEquityInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsTotalMember_019caf13-7184-7f2a-8cf8-bb36bb02336c" xlink:to="loc_ally_NonmarketableEquityInvestmentsMember_019caf13-7184-769a-93df-8874daf32946" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_RepossessedAndForeclosedAssetsMember_019caf13-7184-75d6-a6ec-fc2eaa913f41" xlink:href="ally-20260331.xsd#ally_RepossessedAndForeclosedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsTotalMember_019caf13-7184-7f2a-8cf8-bb36bb02336c" xlink:to="loc_ally_RepossessedAndForeclosedAssetsMember_019caf13-7184-75d6-a6ec-fc2eaa913f41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-7eb6-8dd7-8835464df746" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf13-7184-77a6-af52-af0b5b77aeaa" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-7eb6-8dd7-8835464df746" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-7eb6-8dd7-8835464df746_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-7eb6-8dd7-8835464df746" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-7eb6-8dd7-8835464df746_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-73e6-b95c-ef20115877d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019caf13-7184-7eb6-8dd7-8835464df746" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-73e6-b95c-ef20115877d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019caf13-7184-7868-b0c9-d91b7384d2f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019caf13-7184-73e6-b95c-ef20115877d7" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019caf13-7184-7868-b0c9-d91b7384d2f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019caf13-7184-7376-beb4-7f09c677718a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019caf13-7184-7376-beb4-7f09c677718a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-76ed-965c-71cac6468063" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-76ed-965c-71cac6468063" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_019caf13-7184-7ec2-9241-4bab6575cb12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_019caf13-7184-7ec2-9241-4bab6575cb12" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019caf13-7184-761c-b667-9eb1e6a0aec1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019caf13-7184-761c-b667-9eb1e6a0aec1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_LowerOfCostOrFairValueOrValuationReserveAllowance_019caf13-7184-7065-8214-d15dacc939db" xlink:href="ally-20260331.xsd#ally_LowerOfCostOrFairValueOrValuationReserveAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf13-7184-79b9-a6a4-9c11b6fd504b" xlink:to="loc_ally_LowerOfCostOrFairValueOrValuationReserveAllowance_019caf13-7184-7065-8214-d15dacc939db" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/FairValueScheduleofFairValuebyBalanceSheetGroupingDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#FairValueScheduleofFairValuebyBalanceSheetGroupingDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/FairValueScheduleofFairValuebyBalanceSheetGroupingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019caf13-7184-7285-bdce-684dd5168f8b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019caf13-7184-7285-bdce-684dd5168f8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019caf13-7184-76b2-8c86-61c2ef0015b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019caf13-7184-7285-bdce-684dd5168f8b" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019caf13-7184-76b2-8c86-61c2ef0015b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-76b2-8c86-61c2ef0015b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019caf13-7184-76b2-8c86-61c2ef0015b1" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-76b2-8c86-61c2ef0015b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019caf13-7184-7322-837c-7f869ec94900" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019caf13-7184-76b2-8c86-61c2ef0015b1" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019caf13-7184-7322-837c-7f869ec94900" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-7d3d-a57c-fa72986fa683" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019caf13-7184-7322-837c-7f869ec94900" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-7d3d-a57c-fa72986fa683" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019caf13-7184-7e27-bbc6-553af451bdc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-7d3d-a57c-fa72986fa683" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019caf13-7184-7e27-bbc6-553af451bdc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019caf13-7184-748b-bc43-59babfe993e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019caf13-7184-7d3d-a57c-fa72986fa683" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019caf13-7184-748b-bc43-59babfe993e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-78cd-9c68-8468ad890743" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019caf13-7184-7285-bdce-684dd5168f8b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-78cd-9c68-8468ad890743" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-78cd-9c68-8468ad890743_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-78cd-9c68-8468ad890743" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-78cd-9c68-8468ad890743_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7b33-ba7a-d460d21f53c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf13-7184-78cd-9c68-8468ad890743" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7b33-ba7a-d460d21f53c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-709c-bd15-ecb1534ad7bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7b33-ba7a-d460d21f53c6" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019caf13-7184-709c-bd15-ecb1534ad7bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-75d9-9d2d-42ac6e4ffb93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7b33-ba7a-d460d21f53c6" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019caf13-7184-75d9-9d2d-42ac6e4ffb93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7d49-82b1-d32a18ac719a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf13-7184-7b33-ba7a-d460d21f53c6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019caf13-7184-7d49-82b1-d32a18ac719a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-758c-8d0e-608ca7a7b968" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-758c-8d0e-608ca7a7b968" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019caf13-7184-76f1-8662-53c5b00f4450" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019caf13-7184-76f1-8662-53c5b00f4450" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-7e80-9211-5cbf812636f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019caf13-7184-7e80-9211-5cbf812636f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock_019caf13-7184-7e7f-a65b-6b3456f3b130" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock_019caf13-7184-7e7f-a65b-6b3456f3b130" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Deposits_019caf13-7184-7204-bc19-1e58f08f2d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Deposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_Deposits_019caf13-7184-7204-bc19-1e58f08f2d4d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_019caf13-7184-7730-baef-7cc725167300" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_ShortTermBorrowings_019caf13-7184-7730-baef-7cc725167300" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019caf13-7184-750c-b03a-11a4ebfa86e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019caf13-7184-709d-a1f7-0efb8916bf5a" xlink:to="loc_us-gaap_LongTermDebt_019caf13-7184-750c-b03a-11a4ebfa86e7" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/SegmentInformationDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#SegmentInformationDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/SegmentInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf13-7232-73e6-912e-2792cc12c8d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf13-7232-73e6-912e-2792cc12c8d6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf13-7232-799a-9bf0-684cd06a2fc7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf13-7232-73e6-912e-2792cc12c8d6" xlink:to="loc_srt_ConsolidationItemsAxis_019caf13-7232-799a-9bf0-684cd06a2fc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7232-799a-9bf0-684cd06a2fc7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7232-799a-9bf0-684cd06a2fc7" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7232-799a-9bf0-684cd06a2fc7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf13-7232-71ff-a8e5-64b2d32ca69b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf13-7232-799a-9bf0-684cd06a2fc7" xlink:to="loc_srt_ConsolidationItemsDomain_019caf13-7232-71ff-a8e5-64b2d32ca69b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf13-7232-70dd-9866-1e2eebe0f985" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7232-71ff-a8e5-64b2d32ca69b" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf13-7232-70dd-9866-1e2eebe0f985" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7232-77b6-af86-344520e79240" xlink:href="ally-20260331.xsd#ally_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf13-7232-71ff-a8e5-64b2d32ca69b" xlink:to="loc_ally_CorporateReconcilingItemsAndEliminationsMember_019caf13-7232-77b6-af86-344520e79240" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7232-7e9a-bde9-1417465a216a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf13-7232-73e6-912e-2792cc12c8d6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7232-7e9a-bde9-1417465a216a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7232-7e9a-bde9-1417465a216a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7232-7e9a-bde9-1417465a216a" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7232-7e9a-bde9-1417465a216a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf13-7232-7aca-8ffe-b2478ee1c472" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf13-7232-7e9a-bde9-1417465a216a" xlink:to="loc_us-gaap_SegmentDomain_019caf13-7232-7aca-8ffe-b2478ee1c472" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7232-7a11-bfb6-1459af7be8c0" xlink:href="ally-20260331.xsd#ally_AutomotiveFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7232-7aca-8ffe-b2478ee1c472" xlink:to="loc_ally_AutomotiveFinanceOperationsSegmentMember_019caf13-7232-7a11-bfb6-1459af7be8c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_InsuranceOperationsSegmentMember_019caf13-7232-79a2-ac20-c2ebf0d3093c" xlink:href="ally-20260331.xsd#ally_InsuranceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7232-7aca-8ffe-b2478ee1c472" xlink:to="loc_ally_InsuranceOperationsSegmentMember_019caf13-7232-79a2-ac20-c2ebf0d3093c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7232-76a4-8821-5bbb054583be" xlink:href="ally-20260331.xsd#ally_CorporateFinanceOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf13-7232-7aca-8ffe-b2478ee1c472" xlink:to="loc_ally_CorporateFinanceOperationsSegmentMember_019caf13-7232-76a4-8821-5bbb054583be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_TotalFinancingRevenueAndOtherInterestIncome_019caf13-7232-71f6-9579-6a78f2a7de20" xlink:href="ally-20260331.xsd#ally_TotalFinancingRevenueAndOtherInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_ally_TotalFinancingRevenueAndOtherInterestIncome_019caf13-7232-71f6-9579-6a78f2a7de20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOperating_019caf13-7232-74ae-a094-17ffd584ac77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_InterestExpenseOperating_019caf13-7232-74ae-a094-17ffd584ac77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasesIncomeStatementDepreciationExpenseOnPropertySubjectToOrHeldForLease_019caf13-7232-71d4-82c4-3de70079858e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeasesIncomeStatementDepreciationExpenseOnPropertySubjectToOrHeldForLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_OperatingLeasesIncomeStatementDepreciationExpenseOnPropertySubjectToOrHeldForLease_019caf13-7232-71d4-82c4-3de70079858e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_NetFinancingRevenue_019caf13-7232-7064-b9db-2d936d7ac8e4" xlink:href="ally-20260331.xsd#ally_NetFinancingRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_ally_NetFinancingRevenue_019caf13-7232-7064-b9db-2d936d7ac8e4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019caf13-7232-75df-9e4e-b2c452e344bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_NoninterestIncome_019caf13-7232-75df-9e4e-b2c452e344bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019caf13-7232-7daf-aa96-ec3245d5b86b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_Revenues_019caf13-7232-7daf-aa96-ec3245d5b86b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_FinancingReceivableAndOffBalanceSheetCreditLossExpenseReversalExcludingInterest_019caf13-7232-743e-ba92-50aa04408e4c" xlink:href="ally-20260331.xsd#ally_FinancingReceivableAndOffBalanceSheetCreditLossExpenseReversalExcludingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_ally_FinancingReceivableAndOffBalanceSheetCreditLossExpenseReversalExcludingInterest_019caf13-7232-743e-ba92-50aa04408e4c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019caf13-7232-7659-b2ae-428d93190b65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019caf13-7232-7659-b2ae-428d93190b65" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019caf13-7232-76e6-a1d6-e99d14c0fdee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PolicyholderBenefitsAndClaimsIncurredNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019caf13-7232-76e6-a1d6-e99d14c0fdee" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_019d00bf-80b8-7c1b-85a4-b8adf19c1623" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_019d00bf-80b8-7c1b-85a4-b8adf19c1623" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_OtherNoninterestExpenseAbstract_019caf13-7232-793a-8a87-ef60e0bb3246" xlink:href="ally-20260331.xsd#ally_OtherNoninterestExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_ally_OtherNoninterestExpenseAbstract_019caf13-7232-793a-8a87-ef60e0bb3246" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_019caf13-7232-7419-85c3-95fc5f98fdc9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_OtherNoninterestExpenseAbstract_019caf13-7232-793a-8a87-ef60e0bb3246" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_019caf13-7232-7419-85c3-95fc5f98fdc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_019caf13-7232-79df-a6a3-0cd4305f1e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_OtherNoninterestExpenseAbstract_019caf13-7232-793a-8a87-ef60e0bb3246" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_019caf13-7232-79df-a6a3-0cd4305f1e6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoninterestExpense_019caf13-7232-78c5-b050-d5830a0b769b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoninterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ally_OtherNoninterestExpenseAbstract_019caf13-7232-793a-8a87-ef60e0bb3246" xlink:to="loc_us-gaap_OtherNoninterestExpense_019caf13-7232-78c5-b050-d5830a0b769b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpense_019caf13-7232-73e7-bdc0-81953fddf1ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_NoninterestExpense_019caf13-7232-73e7-bdc0-81953fddf1ed" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019caf13-7232-7017-8dda-35569ff42347" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019caf13-7232-7017-8dda-35569ff42347" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019caf13-7232-74d1-af06-a05b17e7337e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_Assets_019caf13-7232-74d1-af06-a05b17e7337e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019caf13-7232-7e6b-b9c2-c3a92a2789fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf13-7232-7756-bed3-f1915b99b2f5" xlink:to="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019caf13-7232-7e6b-b9c2-c3a92a2789fd" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ally.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="ally-20260331.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.ally.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019d41fe-fcf2-7615-adf8-fb1740f7fe38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_SubsequentEventTable_019d41fe-fcf2-7615-adf8-fb1740f7fe38" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019d41fe-fcf2-7ff0-8f19-ff8369f511c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019d41fe-fcf2-7615-adf8-fb1740f7fe38" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019d41fe-fcf2-7ff0-8f19-ff8369f511c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d41fe-fcf2-7ff0-8f19-ff8369f511c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d41fe-fcf2-7ff0-8f19-ff8369f511c7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d41fe-fcf2-7ff0-8f19-ff8369f511c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d41fe-fcf2-7953-a166-ec9b7a9e3fd8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d41fe-fcf2-7ff0-8f19-ff8369f511c7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d41fe-fcf2-7953-a166-ec9b7a9e3fd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019d41fe-fcf2-71c9-b05c-87a426c837de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019d41fe-fcf2-7953-a166-ec9b7a9e3fd8" xlink:to="loc_us-gaap_SubsequentEventMember_019d41fe-fcf2-71c9-b05c-87a426c837de" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019dd30f-9b04-78da-917e-fb81bffccb95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019d41fe-fcf2-7615-adf8-fb1740f7fe38" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019dd30f-9b04-78da-917e-fb81bffccb95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-78da-917e-fb81bffccb95_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019dd30f-9b04-78da-917e-fb81bffccb95" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-78da-917e-fb81bffccb95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-733d-b51e-62b38c0a04ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019dd30f-9b04-78da-917e-fb81bffccb95" xlink:to="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-733d-b51e-62b38c0a04ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesDPreferredStockMember_019dd30f-9b04-7271-a36d-9c081fefab73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesDPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-733d-b51e-62b38c0a04ae" xlink:to="loc_us-gaap_SeriesDPreferredStockMember_019dd30f-9b04-7271-a36d-9c081fefab73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_019dd30f-9b04-7a5a-a04b-e03d077cdad1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019dd30f-9b04-733d-b51e-62b38c0a04ae" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_019dd30f-9b04-7a5a-a04b-e03d077cdad1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019d41fe-fcf2-7eb7-a9b1-1dba78388c74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019d41fe-fcf2-7eb7-a9b1-1dba78388c74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019de42a-a598-7eac-bd77-27cdff601337" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019de42a-a598-7eac-bd77-27cdff601337" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_019dd30f-9b04-7d22-9edd-48f2e95585f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_019dd30f-9b04-7d22-9edd-48f2e95585f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019dd30f-9b04-7401-9ecf-8e46b84cf515" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019dd30f-9b04-7401-9ecf-8e46b84cf515" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreference_019dd30f-9b04-717f-9b77-aeec01596f78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockLiquidationPreference"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_PreferredStockLiquidationPreference_019dd30f-9b04-717f-9b77-aeec01596f78" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_PreferredStockDividendRateBasisSpreadVariableRate_019dda31-7776-7b0b-b594-36b638781095" xlink:href="ally-20260331.xsd#ally_PreferredStockDividendRateBasisSpreadVariableRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_ally_PreferredStockDividendRateBasisSpreadVariableRate_019dda31-7776-7b0b-b594-36b638781095" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_PreferredStockNumberOfSharesIntendedToBeRedeemed_019dda2e-7986-7b36-9a8a-e26f38373727" xlink:href="ally-20260331.xsd#ally_PreferredStockNumberOfSharesIntendedToBeRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_ally_PreferredStockNumberOfSharesIntendedToBeRedeemed_019dda2e-7986-7b36-9a8a-e26f38373727" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockRedemptionPricePerShare_019dd7fe-b4b9-7491-9a47-918a4af52aad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockRedemptionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_PreferredStockRedemptionPricePerShare_019dd7fe-b4b9-7491-9a47-918a4af52aad" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_PreferredStockNumberOfSharesIntendedToBeRedeemedPercentageOfIssuedAndOutstandingShares_019dd51c-ffb5-7a4a-b67c-b095b341b2a6" xlink:href="ally-20260331.xsd#ally_PreferredStockNumberOfSharesIntendedToBeRedeemedPercentageOfIssuedAndOutstandingShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_ally_PreferredStockNumberOfSharesIntendedToBeRedeemedPercentageOfIssuedAndOutstandingShares_019dd51c-ffb5-7a4a-b67c-b095b341b2a6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreferenceValue_019dd4e9-2c88-7e99-acd6-d00b6d29a004" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockLiquidationPreferenceValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019d41fe-fcf2-7218-9a54-9033a6a5ed33" xlink:to="loc_us-gaap_PreferredStockLiquidationPreferenceValue_019dd4e9-2c88-7e99-acd6-d00b6d29a004" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.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_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest" xlink:type="arc" order="101"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss" xlink:type="arc" order="102"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss" xlink:type="arc" order="103"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementOfCashFlowsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInDeferredIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract" xlink:to="loc_us-gaap_LongTermDebt" xlink:type="arc" order="32"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.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/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_ally_StephanieN.RichardMember_019d9f94-4af4-7ff4-b5ca-38aee7d45413" xlink:href="ally-20260331.xsd#ally_StephanieN.RichardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_ally_StephanieN.RichardMember_019d9f94-4af4-7ff4-b5ca-38aee7d45413" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
