White Mountains Insurance Group Ltd
WTM- Exchange
- NYSE
- Industry
- Fire, Marine & Casualty Insurance
- SEC CIK
- 0000776867
No open-market purchases or sales by White Mountains Insurance Group Ltd insiders were filed in the last 90 days; 356 institutions reported holding it in 13F filings for Q2 2026, worth $4.57B in total; Southeastern Asset Management (Longleaf) is the only superinvestor holding it.
Holders of 5% or more of WTM
Holders whose latest Schedule 13D or 13G filing reports 5% or more of White Mountains Insurance Group Ltd, largest stake first. The change is against the holder's previous filing.
| Holder | Latest form | Stake | Change | First filed | Latest filing | Filing |
|---|---|---|---|---|---|---|
| Morgan Stanley | 13G/A | 5.20%132.6K shares | −1.00 ppfrom 6.20% | Aug 7, 20252 filings | Nov 7, 2025 | SEC |
Stakes are as of each holder's latest filing. Holders whose last filing was in the old format (before December 18, 2024) have no stake on record and are not listed, and after an acquisition or delisting holders usually stop filing.
13D and 13G filings
2 Schedule 13D and 13G filings on White Mountains Insurance Group Ltd, newest first, including old-format filings without a stake.
| Filed (ET) | Filer | Form | Stake | Change | Event date | Filing |
|---|---|---|---|---|---|---|
| Nov 7, 202511:48 AM ET | Morgan Stanley | 13G/A | 5.20%132.6K shares | −1.00 ppfrom 6.20% | Sep 30, 2025 | SEC |
| Aug 7, 20252:59 PM ET | Morgan Stanley | 13G/A | 6.20%159.0K shares | – | Jun 30, 2025 | SEC |
Form 144: proposed insider sales
Notices from officers, directors and other affiliates planning to sell White Mountains Insurance Group Ltd shares.
No Form 144 notices for White Mountains Insurance Group Ltd are on file.