| William VI | |
|---|---|
| Marquis of Montferrat | |
| Reign | 1207–1226 |
| Predecessor | Boniface I, Marquis of Montferrat |
| Successor | Boniface II, Marquis of Montferrat |
| Titular King of Thessalonica | |
| Reign | 1207–1226 |
| Predecessor | Boniface I, Marquis of Montferrat |
| Successor | Boniface II, Marquis of Montferrat |
| Born | c. 1173 |
| Died | 17 September 1225 Almyros |
| Spouse | Berta di Clavesana |
| Issue | Boniface II, Marquis of Montferrat Beatrice of Montferrat, lady of Saint-Bonnet Alice of Montferrat, Queen of Cyprus |
| House | Aleramici |
| Father | Boniface I, Marquis of Montferrat |
| Mother | Helena del Bosco |
William VI (c. 1173 – 17 September 1225) was the tenth Marquis of Montferrat from 1203 and titular King of Thessalonica from 1207.