西蒙斯第一国家公司美股招股说明书(2025-09-10版)

$325,000,000Simmons First National Corporation6.25%Fixed-to-FloatingRate Subordinated Notes due 2035 We are offering $325,000,000 aggregate principal amount of 6.25%fixed-to-floatingrate subordinated notes due 2035 (the “Notes”) pursuant to this prospectus supplementand the accompanying prospectus. The Notes will be offered in minimum denominations of $1,000 and integral multiples of $1,000 in excess thereof. The Notes will mature onOctober 1, 2035 (the “Maturity Date”). From and including the date of original issuance to, but excluding, October 1, 2030 or the date of earlier redemption (the “fixed rateperiod”), the Notes will bear interest at an initial rate of 6.25% per annum, payable semi-annually in arrears on April 1 and October1 of each year, commencing on April 1, 2026.The last interest payment date for the fixed rate period will be October 1, 2030. From and including October 1, 2030 to, but excluding, the Maturity Date or the date of earlierredemption (the “floating rate period”), the Notes will bear interest at a floating rate per annum equal to a benchmark rate(which is expected to be Three-Month Term SOFR (asdefined herein)), plus 302 basis points, payable quarterly in arrears on January 1, April 1, July 1 and October 1 of each year, commencing on January 1, 2031. Notwithstanding theforegoing, in the event that the Three-Month Term SOFR is less than zero, the Three-Month Term SOFR shall be deemed to be zero. We may, at our option, beginning with the interest payment date of October 1, 2030 and on any interest payment date thereafter, redeem the Notes, in whole or in part. TheNotes will not otherwise be redeemable by us prior to maturity, unless certain events occur, as described under “Description of the Notes — Redemption” in this prospectussupplement. The redemption price for any redemption is 100% of the principal amount of the Notes, plus accrued and unpaid interest thereon to, but excluding, the date ofredemption. Any early redemption of the Notes will be subject to the receipt of the approval of the Board of Governors of the Federal Reserve System (the “Federal Reserve”) tothe extent then required under applicable laws or regulations, including capital regulations. The Notes will be unsecured subordinated obligations, will rank pari passu, or equally, with all of our future unsecured subordinated debt and will be junior to all of ourexisting and future senior debt. The Notes will be structurally subordinated to all existing and future liabilities of our subsidiaries and will be effectively subordinated to ourexisting and future secured indebtedness. There will be no sinking fund for the Notes. The Notes will be obligations of Simmons First National Corporation only and will not beobligations of, and will not be guaranteed by, any of Simmons First National Corporation’s subsidiaries. For a more detailed description of the Notes, see “Description of theNotes.” Prior to this offering, there has been no public market for the Notes. The Notes will not be listed on any securities exchange or included in any automated quotation system. The Notes are not savings accounts, deposits or other obligations of any of our bank ornon-banksubsidiaries, and are not insured or guaranteed by the FederalDeposit Insurance Corporation (the “FDIC”) or any other governmental agency. The Notes are ineligible as collateral for a loan or extension of credit from SimmonsFirst National Corporation or any of its subsidiaries. None of the U.S. Securities and Exchange Commission (the “SEC”), any state securities commission or bankingagency, the FDIC, the Board of Governors of the Federal Reserve or any other regulatory body has approved or disapproved of the Notes or passed upon the accuracy oradequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense. Investing in the Notes involves risks. Before investing in the Notes, potential purchasers of the Notes should consider the information set forth in the “RiskFactors” section beginning onpageS-11,in our Annual Report on Form10-Kfor the year ended December31, 2024 and in our Quarterly Report on Form10-Qfor thequarter ended June30, 2025, which are incorporated herein by reference. The underwriters expect to deliver the Notes to purchasers in book-entry form through the facilities of The Depository Trust Company (“DTC”), against payment therefor inimmediately available funds, on or about September 12, 2025, which is the third business day following the date of pricing the Notes (such settlement being referred to as “T+3”).See “Underwriting” for details. Morgan Stanley Co-Managers Table of Contents TABLE OF CONTENTS Prospectus Supplement About This Prospectus Supplement and the Accompanying ProspectusWhere You Can Find More InformationIncorporation by ReferenceCautionary Note Regarding Forward-Looking StatementsSummaryRisk FactorsUse of ProceedsUnaudited Pro Forma Financial InformationCapitalizatio