UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ☐ 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 1-8993 WHITE MOUNTAINS INSURANCE GROUP, LTD. (Exact name of Registrant as specified in its charter) Bermuda (State or other jurisdiction of incorporation or organization) 94-2708455 23 South Main Street, Suite 3B (I.R.S. Employer Identification No.) Hanover, 03755-2053 (Address of principal ...