Reg FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934   August 4, 2025 Date of Report (Date of earliest event reported) TRUSTMARK CORP ORATION (Exact name of registrant as specified in its charter)   Mississippi   000-03683   64-0471500 (State or other jurisdiction of incorporation)   (Commission File Number)   (IRS Employer Identification No.)   248 East Capitol Street , Jackson , Mississippi   39201 (Address of principal executive offices)   (Zip Code)       Registrant’s telephone number, including area code:   ( 601 ) 208-5111   Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:   ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))   Securities registered Pursuant to Section 12(b) of the Act: Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, no par value TRMK Nasdaq Global Select Market   Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).   Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐         Item 7.01. Regulation FD Disclosure.   On August 4, 2025, Trustmark Corporation’s principal subsidiary, Trustmark National Bank, converted from a national banking association to a Mississippi-chartered banking corporation and changed its name to Trustmark Bank after receiving all necessary regulatory approvals from the Federal Reserve and the Mississippi Department of Banking and Consumer Finance. Trustmark Bank is a member bank of the Federal Reserve System and is supervised by the Federal Reserve Bank of Atlanta and the Mississippi Department of Banking and Consumer Finance. The charter conversion will not affect the bank’s customers’ day-to-day experience with Trustmark, and customer deposits continue to be insured by the Federal Deposit Insurance Corporation to the greatest extent permitted by law.       SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.   TRUSTMARK CORPORATION BY:   /s/ Thomas C. Owens     Thomas C. Owens     Treasurer and Principal Financial Officer       DATE:   August 4, 2025