Dividends on the SeriesD Preferred Stock will not be cumulative. If Ally’s board of directors or a duly authorized committee of its board does notdeclare a dividend on the SeriesD Preferred Stock in respect of a dividend period, then no dividend shall be deemed to have accrued for such dividendperiod, be payable on the applicable dividend payment date, or be cumulative, and Ally will have no obligation to pay any dividend for that dividend period,whether or not its board of directors or a duly authorized committee of its board declares a dividend on the SeriesD Preferred Stock for any future dividendperiod. The SeriesD Preferred Stock has no stated maturity, is not subject to any mandatory redemption, sinking fund or other similar provisions and willremain outstanding unless redeemed at Ally’s option. Ally may, at its option, redeem the SeriesD Preferred Stock (i)in whole or in part, from time to time,on any dividend payment date on or after August15, 2031 or (ii)in whole, but not in part, at any time within 90 days following certain changes to regulatorycapital requirements as described herein, in each case, at a redemption price equal to $1,000 per share, plus any declared and unpaid dividends to, butexcluding, the date of redemption, without accumulation of undeclared dividends. Any redemption of the SeriesD Preferred Stock is subject to priorapproval of the Board of Governors of the Federal Reserve System, which we refer to as the Federal Reserve. The SeriesD Preferred Stock will not be listed or displayed on any securities exchange or interdealer market quotation system. The SeriesD Preferred Stock will rank equally with our outstanding 4.700% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, SeriesB(the “Series B Preferred Stock”) and 4.700% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series C (the “Series C Preferred Stock”). TheSeriesD Preferred Stock will not have any voting rights, except in limited circumstances as described under “Description of SeriesD Preferred Stock—Voting Rights” on pageS-21. Investing in the SeriesD Preferred Stock involves risks. See “Risk Factors” beginning on pageS-12 to read about risks youshould consider before buying the SeriesD Preferred Stock. PerShareTotalPrice to public(1)$ 1,000.00$ 1,000,000,000Underwriting discount$10.00$10,000,000Proceeds, before expenses, to Ally$990.00$990,000,000 (1)Plus declared dividends, if any, on the Series D Preferred Stock from May 1, 2026, to the date of delivery. The SeriesD Preferred Stock is not a savings or deposit account of Ally or any of its bank or non-bank subsidiaries and is not insured by theFederal Deposit Insurance Corporation or any other government agency or insurer. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities ordetermined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminaloffense. TABLE OF CONTENTS Prospectus Supplement Cautionary Statement Regarding Forward-Looking StatementsIndustry and Market DataSummaryRisk FactorsUse of ProceedsCapitalizationDescription of SeriesD Preferred StockCertain Benefit Plan and IRA ConsiderationsMaterial United States Federal Income Tax ConsiderationsUnderwritingIncorporation by Reference; Where You Can Find More InformationValidity of the SecuritiesIndependent Registered Public Accounting Firm Prospectus About This ProspectusInformation Incorporated by Reference; Where You Can Find More Information Cautionary Statement Regarding Forward-Looking Statements SummaryRisk FactorsUse of ProceedsDescription of Senior NotesDescription of Subordinated Notes Description of Preferred Stock Book-Entry, Delivery and Forms of Notes and Depositary Shares Plan of Distribution Validity of Securities Experts We provide information to you about this offering in two separate documents. The accompanying prospectus provides generalinformation about us and the securities we may offer from time to time. This prospectus supplement describes the specific details regarding thisoffering. Additional information is incorporated by reference in this prospectus supplement. If information in this prospectus supplement isinconsistent with the accompanying prospectus, you should rely on this prospectus supplement. Neither we nor the underwriters have authorized anyone to provide any information other than that contained or incorporated byreference in this prospectus supplement, the accompanying prospectus or any free writing prospectus prepared by or on behalf of us or towhich we have referred you. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any otherinformation that others may give you. We are not, and the underwriters are not, making an offer of the SeriesD Preferred Stock in anyjurisdiction where the offer is not permitted. You should not assu