SECURITIES AND EXCHANGE COMMISSION Form 10-K For the fiscal year ended December 31, 2020 W. R. BERKLEY CORPORATION 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 5.900% Subordinated Debentures due 2056 WRB-PC New York Stock Exchange 5.750% Subordinated Debentures due 2056 WRB-PD 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 Washington, D.C. 20549 (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 or 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ______ to ______. Commission file number 1-15202 Delaware (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) 475 Steamboat Road Greenwich, CT 22-1867895 (I.R.S. Employer Identification Number) 06830 (Zip Code) Registrant’s telephone number, including area code: (203) 629-3000 Securities registered pursuant to Section 12(b) of the Act: (Address of principal executive offices) Securities registered pursuant to Section 12(g) of the Act: None Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.   Yes ☒ No ☐ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act.   Yes ☐ No ☒ Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐