Avesgaud de Bellême was a son of Yves de Bellême and Godeheu. His maternal uncle was Seinfroy, Bishop of Le Mans, who he succeeded about 997. His bishopric was centered on St. Julian of Le Mans. Both Seinfroy and Avesgaud belonged to the powerful and independent House of Bellême which controlled the borders of Perche, Séez and Alençon between the Île-de-France and Normandy. The Bellêmes were not considered loyal to either Normandy or the French king. Seinfroy, however, had been an adherent of Geoffrey I, Count of Anjou to whom he owed his appointment to the see of Le Mans. For possibly the same reason Avesgaud was aligned with Count Fulk as well. The first years of his reign as bishop were quiet until Herbert became Count of Maine about 1017. From that time on the two were locked in a bitter and endless struggle. Avesgaud resisted all forms of comital control from Herbert Wake-dog and in addition to his own forces enlisted help from a knight named Herbrannus paying him with lands from the church estates. However Herbrannus failed to defend the Bishop against Count Herbert. During his long wars with Count Hebert I of Maine, the count attacked and destroyed Avesgaud's castle at Duneau causing Avesgaud to flee to the protection of his brother William's castle at Bellême. Once he was safe the Bishop excommunicated Herbert and then continued his warring against with him. Not long after the excommunication was lifted and peace was restored between them, Herbert started raiding the Bishop’s estates again. When Herbert learned the Bishop had built a castle at La Ferté-Bernard he attacked Avesgaud there causing the Bishop to flee again, but this time the castle was repaired. On the last occasion Avesgaud was forced to leave his see he traveled to the Holy Land on a pilgrimage. He is said to have died c. 1036 at Verdun on his return to Le Mans.
Family
He was succeeded as bishop of Le Mans by his nephew Gervais de Château-du-Loir, son of his sister Hildeburge de Bellême. His brother, Yves de Bellême, was the Abbot of Fleury. Another nephew, Ives, son of his brother William was Seigneur de Bellême and Bishop of Sées.
