Company Update

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   December 2, 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 8.01. Other Events .   Trustmark Corporation (the "Company") announced that, effective January 1, 2026, the Board of Directors has authorized a new stock repurchase program under which up to $100.0 million of its outstanding common shares may be acquired through December 31, 2026. The adoption of the Company’s share repurchase program follows the notification of the new share repurchase program by the Company to the Board of Governors of the Federal Reserve System. This authorization replaces the Company’s prior stock repurchase program, which will expire in accordance with its terms on December 31, 2025. The shares may be purchased from time to time at prevailing market prices, through open market or privately negotiated transactions, depending on market conditions. There is no guarantee as to the number or aggregate market value of shares that may be repurchased by the Company, and the Company may discontinue purchases at any time at management’s discretion. As of October 31, 2025, the Company had 59,958,255 shares outstanding.       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:   December 3, 2025