FALSE0000776867Bermuda1-899394-270845503755☐☐☐☐☐00007768672025-01-082025-01-08

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

January 8, 2025

Date of Report (Date of earliest event reported)

WHITE MOUNTAINS INSURANCE GROUP, LTD.

(Exact name of registrant as specified in its charter)

Bermuda (State or other jurisdiction of  incorporation or organization)			1-8993 (Commission file number)			94-2708455 (I.R.S. Employer Identification No.)

23 South Main Street, Suite 3B, Hanover, New Hampshire 03755

(Address of principal executive offices)

(603) 640-2200

(Registrant’s telephone number, including area code)

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 Shares, par value $1.00 per share

WTM

New York Stock Exchange

WTM.BH

Bermuda 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.      o

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ITEM 8.01 Other Events.

White Mountains Insurance Group, Ltd. (NYSE: WTM) (“White Mountains”) announced today that Ark Insurance Holdings Limited (“Ark”), its specialty property and casualty reinsurance and insurance subsidiary, has renewed Outrigger Re Ltd. ("Outrigger") for business incepted during calendar year 2025. The renewal is on similar terms as were in effect for calendar year 2024.

Outrigger, a reinsurance sidecar, has again entered into a quota share with Ark to provide collateralized reinsurance protection on a portion of Ark Bermuda's global property catastrophe portfolio beginning on January 1, 2025.

Outrigger received $230 million of total investor capital for January 1, including $150 million from White Mountains. The remaining capital was provided by continuing third-party investors.

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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 thereunto duly authorized.

WHITE MOUNTAINS INSURANCE GROUP, LTD.

Date: January 8, 2025

By:

/s/   MICHAELA J. HILDRETH            Michaela J. Hildreth       Managing Director and       Chief Accounting Officer

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