花旗集团美股招股说明书(2025-10-15版)

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statementrelating to these securities has been filed with the Securities and Exchange Commission. This preliminary prospectussupplement and the accompanying prospectus are not an offer to sell, nor do they seek an offer to buy, securities in anyjurisdiction where the offer or sale is not permitted. The notes will mature on October, 20. The notes will bear interest (i)from, and including, the date of issuance of the notes to, but excluding,October, 20(the “Fixed Rate Period”), at a fixed rate equal to% per annum, payable annually in arrears on each October,commencing on October, 2026, and (ii)from, and including, October, 20(the “Floating Rate Period”), at an annual rate equal to EURIBOR (asdefined on page33 of the accompanying prospectus) plus%, payable quarterly in arrears on each January, April, Julyand October,beginning on January, 20. Citigroup may redeem the notes (i)in whole at any time or in part from time to time, on or after April, 2026 (or, if additional notes are issuedafter October, 2025, beginning six months after the issue date of such additional notes) and prior to October, 20, (ii) in whole, but not in part, onOctober, 20and (iii)in whole at any time or in part from time to time, on or after September, 20, at the applicable redemption price describedunder “Description of Notes” below. In addition, Citigroup may redeem the notes prior to maturity if changes involving United States taxation occurwhich could require Citigroup to pay additional amounts, as described under “Description of Debt Securities—Payment of Additional Amounts” and “—Redemption for Tax Purposes” in the accompanying prospectus. The notes are being offered globally for sale in the United States, Europe, Asia and elsewhere where it is lawful to make such offers. Applicationwill be made to list the notes on the regulated market of the Luxembourg Stock Exchange, but Citigroup cannot assure you that the notes will beapproved for listing and is not required to maintain this listing. See “Description of Notes—Listing” below. Investing in the notes involves a number of risks. See the “Risk Factors” section beginning on page8 of the accompanying prospectus,where specific risks associated with the notes are described, and the factors listed and described under “Risk Factors” in our annual report onForm10-Kfor the year ended December31, 2024, along with the other information in, or incorporated by reference in, this prospectussupplement and the accompanying prospectus before you make your investment decision. Neither the Securities and Exchange Commission nor any state securities commission nor the Luxembourg Stock Exchange has approved ordisapproved of these notes or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation tothe contrary is a criminal offense. Public Offering Price Interest on the notes will accrue from October, 2025. Net proceeds to Citigroup (after expenses) are expected to be approximately € October, 2025 Table of Contents TABLE OF CONTENTSPageProspectus SupplementForward-Looking StatementsS-4Description of NotesS-5UnderwritingS-8Conflicts of InterestS-9Legal OpinionsS-12ProspectusProspectus Summary1Forward-Looking Statements8Risk Factors Related to Floating Rate Debt Securities8Citigroup Inc.12Use of Proceeds and Hedging15European Monetary Union16Description of Debt Securities16United States Federal Income Tax Considerations50Currency Conversions and Foreign Exchange Risks Affecting Debt Securities Denominated in a Foreign Currency57Description of Common Stock Warrants59Description of Index Warrants61Description of Capital Stock64Description of Preferred Stock83Description of Depositary Shares86Description of Stock Purchase Contracts and Stock Purchase Units89Plan of Distribution90ERISA Considerations93Legal Matters95Experts95 The Luxembourg Stock Exchange takes no responsibility for the contents of this document, makes no representation as to its accuracy orcompleteness and expressly disclaims any liability whatsoever for any loss howsoever arising from or in reliance upon the whole or any part ofthe contents of this prospectus supplement and the accompanying prospectus. The distribution or possession of this prospectus supplement and the accompanying prospectus in or from certain jurisdictions may be restrictedby law. Persons into whose possession this prospectus supplement and the accompanying prospectus come are required by Citigroup and theunderwriters to inform themselves about, and to observe any such restrictions, and neither Citigroup nor any of the underwriters accepts any liability inrelation thereto. See “Underwriting.” Table of Contents In connection with this issue, Citigroup Global Markets Limited as stabilizing manager (or persons acting on behalf of the stabilizing manager)may over-allot notes (provided thatthe aggreg