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): December 5, 2025 Commission File Number 1-15202     W. R. BERKLEY CORPORATION (Exact name of registrant as specified in its charter)       Delaware   22-1867895 (State or other jurisdiction of incorporation or organization)   (I.R.S. Employer Identification No.)   475 Steamboat Road   Greenwich   Connecticut   06830 (Address of principal executive offices)       (Zip Code) (203) 629-3000 (Registrant’s telephone number, including area code) None (Former name, former address and former fiscal year, 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, par value $.20 per share   WRB   New York Stock Exchange 5.700% Subordinated Debentures due 2058   WRB-PE   New York Stock Exchange 5.100% Subordinated Debentures due 2059   WRB-PF   New York Stock Exchange 4.250% Subordinated Debentures due 2060   WRB-PG   New York Stock Exchange 4.125% Subordinated Debentures due 2061   WRB-PH   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 December 5, 2025, W. R. Berkley Corporation (the “Company”) issued a press release announcing that the Company has been informed by representatives of Mitsui Sumitomo Insurance Co., Ltd. (“MSI”) that MSI has acquired beneficial ownership of at least 12.5% of the Company’s outstanding common stock (the “Common Stock”) pursuant to MSI’s previously announced agreements with a company owned by members of the Berkley family and trusts for their benefit. The press release is attached as Exhibit 99.1 and incorporated by reference.   Item 9.01. Financial Statements and Exhibits. (d) Exhibits.   Exhibit No.    Description 99.1    Press Release, issued December 5, 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.   W. R. BERKLEY CORPORATION By:   /s/ Richard M. Baio   Name:   Richard M. Baio   Title:   Executive Vice President – Chief Financial Officer Date: December 5, 2025