William, Count of Sully

Who was William, Count of Sully?

William, Count of Sully, also known as William the Simple was Count of Blois and Count of Chartres from 1102 to 1107, and jure uxoris Count of Sully. William was the eldest son of Stephen-Henry, Count of Blois and Adela of Normandy, daughter of William the Conqueror. He was the older brother of Theobald II, Count of Champagne, King Stephen of England and Henry, Bishop of Winchester.

In the absence of male issue to Henry I, William was the eldest legitimate male heir of the line of William the Conqueror. He would thus have been the principal rival to Henry's daughter Matilda to inherit the throne after Henry's death. However, he was not considered as a candidate for the English crown. Several historians have taken the view that he was passed over because of mental deficiency; hence his soubriquet "William the Simple". Though widely argued, this has never been clearly substantiated.

William was at first groomed to inherit the comptal throne as Count of Blois and Chartres, and was designated count shortly before his father's departure on his second crusade in 1102. However he was soon removed from wide ranging comptal duties by his mother, because of his erratic behaviour.