Annual Report of Employee Stock Plans (11-k)

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

_________________

FORM 11-K

(Mark One)

 ANNUAL REPORT PURSUANT TO SECTION 15( D ) OF THE Securities EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2018

o TRANSITION REPORT PURSUANT TO SECTION 15(D) OF THE Securities EXCHANGE ACT OF 1934

For the transition period from ____________ to ______________

Commission file number : 1-8993

A. Full title of the plan and the address of the plan, if different from that of the issuer named

below:

White Mountains Retirement Plan

B. Name of issuer of the securities held pursuant to the plan and the address of its principal

executive office:

White Mountains Insurance Group, Ltd.

80 South Main Street

Hanover, NH 03755

REQUIRED INFORMATION

1. Not applicable.

2. Not applicable .

3. Not applicable.

4. The White Mountains Retirement Plan (the "Plan"), is subject to the requirements of the Employee Retirement lncome Security Act of 1974 ("ERISA"). Pursuant to Section 103(c) of ERISA and the regulations thereunder, the Plan is not required to file audited financial statements because the Plan has fewer than 100 participants. Attached hereto is a copy of the Plan's Summary Annual Report and Schedule I to the Form 5500 that the Plan has filed with the Employee Benefits Security Administration.

Summary Annual Report and Schedule I to the Form 5500

SIGNATURES

The Plan . Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.