See also
| Husband: | William + of MOHUN (1090-1155) | |
| Wife: | Agnes + of GAUNT (c. 1095-1155) | |
| Children: | William + of MOHUN (c. 1115- ) | |
| Name: | William + of MOHUN | |
| Sex: | Male | |
| Father: | - | |
| Mother: | - | |
| Birth | 1090 | |
| Death | 1155 (age 64-65) | |
| Name: | Agnes + of GAUNT | |
| Sex: | Female | |
| Father: | Walter + of GAUNT (c. 1070- ) | |
| Mother: | - | |
| Birth | 1095 (est) | |
| Death | 1155 (age 59-60) | |
| Name: | William + of MOHUN | |
| Sex: | Male | |
| Spouse: | Godehaut + of TOENI ( -1186) | |
| Birth | 1115 (est) | |
| Occupation | Earl of Somerset/Dorset | |
William de Mohun of Dunster (c. 1090 – c. 1155) was a favourite of Empress Matilda and a loyal supporter of her in the war against King Stephen, during which he earned the epithet of the "Scourge of the West". Empress Matilda conferred upon him the title Earl of Somerset, in 1141. In the foundation charter of the priory at Bruton he describes himself as "Willielmus de Moyne, comes Somersetensis". Unlike Baldwin de Redvers who was created Earl of Devon by Matilda at around the same time, William's title was not recognised by Stephen or Henry II, Matilda's son, and his descendants did not use the title.
William was the son of William de Moion, who was seigneur of Moyon which is close to Saint-Lô. the elder William was sheriff of Somerset in 1084.
During the war between Matilda and Stephen, Stephen marched against Mohun's castle at Dunster, but finding it too hard to take, he left Henry de Tracy to keep Mohun under siege.
William married Agnes de Gaunt, daughter of Walter de Gaunt and Maud of Brittany, daughter of Stephen I, Count of Brittany