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 Date of Report (Date of earliest event reported): September 8, 2025   KIRBY CORPORATION (Exact name of registrant as specified in its charter)   Nevada 1-7615 74-1884980 (State or Other Jurisdiction of Incorporation) (Commission File Number) (IRS Employer Identification No.)           55 Waugh Drive , Suite 1000   Houston , Texas   77007 (Address of Principal Executive Offices)   (Zip Code)   Registrant’s telephone number, including area code: 713 - 435-1000   Not Applicable (Former Name or Former Address, if Changed Since Last Report) 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 KEX New York Stock Exchange Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter). 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. On September 8, 2025, the Board of Directors of Kirby Corporation (the “Company”) authorized the repurchase of up to an additional 8,000,000 shares of the Company’s common stock under the Company’s existing share repurchase authorization (the “Repurchase Authorization”). As of September 5, 2025, 4,151,058 shares had been purchased under the Repurchase Authorization and with the new authorization, 8,848,942 shares remained authorized for repurchase. Purchases under the Repurchase Authorization may be made from time to time in the open market, through privately negotiated transactions, block transactions or by other means, including Rule 10b5-1 trading plans, in accordance with applicable securities laws and regulations, including Rule 10b-18 under Securities Exchange Act of 1934, as determined by the Company. The Repurchase Authorization does not obligate the Company to acquire any particular amount of common stock. Future repurchases, if any, will depend on factors such as levels of cash generation from operations, cash requirements for investment in the Company’s business, repayment of future debt, if any, then current stock price, market conditions, securities law limitations and other factors. The Repurchase Authorization may be suspended, modified or discontinued at any time, but the authorization is of an open-ended term. Item 9.01. Financial Statements and Exhibits (d) Exhibits   EXHIBIT INDEX   Exhibit Number   Description of Exhibit         99.1   Press release dated September 8, 2025 104   Cover Page Interactive Data File (embedded within the Inline XBRL document)       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.       KIRBY CORPORATION         Date: September 8, 2025 By: /s/ Raj Kumar       Raj Kumar Executive Vice President and Chief Financial Officer