三井住友金融美股招股说明书(2026-06-29版)

The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. Thispreliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer tobuy these securities in any jurisdiction where the offer or sale is not permitted. SUBJECT TO COMPLETION, DATED JUNE 29, 2026 PRELIMINARY PROSPECTUS SUPPLEMENT(To prospectus dated January11, 2024) Sumitomo Mitsui Financial Group, Inc. (incorporated under the laws of Japan with limited liability)U.S.$ Senior Callable Fixed-to-Floating Rate NotesSenior Callable Floating Rate Notes The senior callable fixed-to-floating rate notes due, or the fixed-to-floating rate notes, will bear interest (i)from and including, 2026 to but excluding the date that is one year prior to thematurity date at a fixed rate of%per annum, payable semiannually in arrears onandof each year, beginning on, 2027, and (ii)from and including the date that is one year prior to thematurity date to but excluding the maturity date, at a floating rateper annum, equal to Compounded Daily SOFR (determined as provided under “Description of the Notes—Calculation of Floating Interest Rates”)plus%, reset quarterly, payable quarterly in arrears on,,andduring the one-year period ending on the maturity date, beginning on, 20, subject to adjustments. The senior callable floating rate notes due, or the floating rate notes, and together with the fixed-to-floating rate notes, the notes, will bear interest commencing, 2026 at a floating rateperannum, equal to Compounded Daily SOFR (determined as provided under “Description of the Notes—Calculation of Floating Interest Rates”) plus%, reset quarterly, payable quarterly in arrears on,,andof each year, beginning on, 2026, subject to adjustments. Each series of the notes may be redeemed (i)on the date that is one year prior to the maturity date of such series of notes, as described under “Description of the Notes—Optional Redemption,” or (ii)at any timeprior to maturity in the circumstances described under “Description of the Notes—Redemption for Taxation Reasons.” The notes will not be subject to any sinking fund. The notes will be issued only in registered formin minimum denominations of U.S.$200,000 and integral multiples of U.S.$1,000 in excess thereof. We have made an application to the Luxembourg Stock Exchange to list the notes on the official list of the Luxembourg Stock Exchange and for such notes to be admitted to trading on the Luxembourg StockExchange’s Euro MTF Market. The Luxembourg Stock Exchange’s Euro MTF Market is not a regulated market for the purposes of Directive 2014/65/EU. This prospectus supplement with the accompanyingprospectus constitutes a prospectus for purposes of Part IV of the Luxembourg law on prospectuses for securities dated July16, 2019. This prospectus supplement and the accompanying prospectus do not constitute a prospectus for the purposes of Regulation (EU) 2017/1129 (as amended, the “Prospectus Regulation”) nor do they constitute aprospectus for the purposes of the Public Offers and Admissions to Trading Regulations 2024 (the “POAT Regulations”) or the Admission to Trading on a Regulated Market Sourcebook of the FCA Handbook in theUK. Investing in the notes involves risks. You should carefully consider the risk factors set forth in “Item 3. Key Information—Risk Factors” of our most recent annual report onForm 20-F filed with the U.S. Securities and Exchange Commission, or the SEC, and in the “Risk Factors” section beginning on page S-11 of this prospectus supplement beforemaking any decision to invest in the notes. (1)Plus accrued interest from, 2026, if settlement occurs after that date.(2)For additional underwriting compensation information, see “Underwriting (Conflicts of Interest).” Neither the SEC nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplementor the related prospectus. Any representation to the contrary is a criminal offense. The notes of each series will be represented by one or more global certificates deposited with a custodian for, and registered in the name of a nominee of, The Depository Trust Company, or DTC. Beneficialinterests in these global certificates will be shown on, and transfers thereof will be effected through, records maintained by DTC and its direct and indirect participants, including Euroclear Bank SA/NV, or Euroclear,and Clearstream Banking S.A., or Clearstream. Except as described in this prospectus supplement or the accompanying prospectus, notes in definitive certificated form will not be issued in exchange for globalcertificates. Table of Contents TABLE OF CONTENTS Prospectus Supplement Prospectus Supplement SummaryRisk FactorsUse of ProceedsCapitalization and IndebtednessSelected Financial and Other Information (IFRS)Supplemental Financial and Other Inf