# White Mountains Insurance Group (WTM): who owns it

2 value investors held White Mountains Insurance Group in their Q3 2026 13F, led by Southeastern Asset Management, Horizon Kinetics.

## 13F holders

| Manager | Portfolio | Value | Change | Quarters held |
| --- | --- | --- | --- | --- |
| Southeastern Asset Management | 1.9% | $35.5m | Trimmed -9.3% | 19 |
| Horizon Kinetics | 0.3% | $25.3m | Trimmed -6.9% | 9 |

Source: SEC filings, via moatshark (https://www.moatshark.com/s/wtm). Values traded and returns are estimates. Not investment advice. Built 2026-10-21.