As of November 6, 2026, White Mountains Insurance Group Ltd. is a publicly traded company (NYSE: WTM); its largest reported holder is Vanguard, with 5.18% on Schedule 13G of April 30, 2026 (Schedule 13G, April 30, 2026).
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Is White Mountains Insurance Group Ltd. a real, registered company?
- White Mountains Insurance Group Lt files with the SEC under CIK 776867 (its SEC filings).
- Its shares are listed under the ticker WTM on NYSE (SEC company record).
- Incorporated in D0; business address in Hanover, New Hampshire, as its SEC filings state.
- Court and bankruptcy records: see Before you sign or pay below.
Before you sign or pay
- Court and bankruptcy: No federal court case or bankruptcy filing found under WHITE MOUNTAINS INSURANCE GROUP LT in our court records and SEC 8-K records (as of 2026-11-06).
- Leadership changes: the latest reported is Stephen Klar, Director (Form 8-K filed 2026-08-27). Check you are dealing with the people now in charge.
- Ownership: 5%+ holders are reported on Schedule 13D or 13G; the latest names Vanguard (filed 2026-04-30).
Who are White Mountains Insurance Group Ltd.'s owners and officers?
White Mountains Insurance Group Ltd.: business address in Hanover, New Hampshire; industry Fire, Marine & Casualty Insurance (Form D, 2026-08-27).
| Report | Holder | Share |
|---|---|---|
| Schedule 13G/A, 2026-05-07 | Neuberger Berman Group LLC | 4.9% |
| Schedule 13G, 2026-04-30 | Vanguard Capital Management | 5.18% |
| Schedule 13G/A, 2026-03-27 | The Vanguard Group | 0% |
| Schedule 13G/A, 2026-02-12 | Morgan Stanley | 3% |
| Schedule 13G, 2026-02-05 | Neuberger Berman Group LLC | 5.1% |
| Schedule 13G/A, 2025-11-07 | Morgan Stanley | 5.2% |
| Schedule 13G/A, 2025-08-07 | Morgan Stanley | 6.2% |
Questions about who owns White Mountains Insurance Group Ltd.
Who owns White Mountains Insurance Group Ltd.?
On this page, one holder's latest ownership filing reports 5% or more of White Mountains Insurance Group Ltd.: Vanguard Capital Management (5.18%, Schedule 13G, filed 2026-04-30).
When did Vanguard Capital Management buy into White Mountains Insurance Group Ltd.?
The filings give report dates, not purchase dates. The earliest filing from Vanguard Capital Management on this page is the Schedule 13G, filed 2026-04-30, reporting 5.18%.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 7 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
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| Filed | Person | Role | Change | Effective |
|---|---|---|---|---|
| Form 8-K, 2026-08-27 | Stephen Klar | Director | appointed |
Which insiders own White Mountains Insurance Group Ltd. shares?
Directors, officers and holders of 10% or more report their shares on Forms 3, 4 and 5. Each line is the latest such report, largest holding first.
- White Mountains Insurance Group Ltd., a 10% owner: 12,356,223 shares, held indirectly (the form names the holder only in its footnotes), on a joint filing (Form 4, 2026-11-05).
- WM Hinson (Bermuda) Ltd., a 10% owner: 12,356,223 shares, held indirectly (the form names the holder only in its footnotes), on a joint filing (Form 4, 2026-11-05).
- , the general counsel and executive vice president: 20,944 shares (0.88% of shares outstanding), 20,357 held directly and 587 indirectly (Form 4, 2026-03-20).
- , the chief executive and a director: 19,356 shares (0.81% of shares outstanding), 19,234 held directly and 122 indirectly (Form 4, 2025-12-22).
- , a director: 10,694 shares (0.45% of shares outstanding), 10,575 held directly and 119 indirectly (Form 4, 2026-05-22).
Shares outstanding: 2,386,823 as of 2026-11-02, from the company's latest SEC cover page.
How much has White Mountains Insurance Group Ltd. raised?
Acquisitions reported on Form 8-K, Item 2.01: completed an acquisition (2025-12-08).
Keep reading
More on White Mountains Insurance Group Ltd. and the records around it.
White Mountains Insurance Group Ltd. elsewhere on the record
- Leadership changes Aug 2026
Companies that share a holder
- Neuberger Berman Group LLC also filed stake reports on 37 other companies: Stock Yards Bancorp, Inc. (Nov 2026), TRANSCAT INC (Nov 2026), Hagerty Inc CLass A (Oct 2026)
- Morgan Stanley also filed stake reports on 182 other companies: MDA Space Ltd. (Nov 2026), RiverNorth/DoubleLine Strategic Opportunity Fund, Inc. (Oct 2026), Arbutus Biopharma Corp (Oct 2026)
- Vanguard Capital Management also filed stake reports on 1495 other companies: A10 Networks Inc (Oct 2026), Altisource Portfolio Solutions SA (Oct 2026), Alto Neuroscience Inc (Oct 2026)
Related pages
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