William IX, Count of Poitiers

William (17 August 1153 – 2 December 1156) was the first son of Henry II, King of England and Eleanor of Aquitaine.[1] He was born in Normandy on the same day that his father's rival, Eustace IV of Boulogne, died.

William IX
William IX, from an early 14th century genealogical tree British Library Royal MS 14 B VI.
Count of Poitiers
Reign	1153–1156
Born	17 August 1153 Normandy, France
Died	2 December 1156 (aged 3) Wallingford Castle, Berkshire
Burial	Reading Abbey, Berkshire
House	Plantagenet / Angevin
Father	Henry II of England
Mother	Eleanor of Aquitaine

William died in 2 December 1156,[lower-alpha 1] aged three.[3][4] This was due to a seizure at Wallingford Castle, and he was buried in Reading Abbey at the feet of his great-grandfather Henry I.[2]

At the time of his death, William was reigning as Count of Poitiers, as his mother had ceded the county to him. For centuries, the dukes of Aquitaine had held this as one of their minor titles, so it had passed to Eleanor from her father; giving it to her son was effectively a revival of the title, separating it from the duchy. Some authorities say he also held the title of "Archbishop of York", but this is probably an error. His half-brother Geoffrey (died 1212), who was born a year before William, later held that office, causing the confusion.