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

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

William either died aged 3 on 2 December 1156,^[2][3] or aged 2 in April 1156.^[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.^[4]

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.

Burial site at Reading Abbey of William IX with his great-grandfather Henry I Beauclerc.

References

Sources

• Baxter, Ron (2016). The Royal Abbey of Reading. The Boydell Press.
• Huscroft, Richard (2016). Tales From the Long Twelfth Century: The Rise and Fall of the Angevin Empire. Yale University Press.
• Strickland, Matthew (2007). "On the Instruction of a Prince: The Upbringing of Henry, the Young King". In Harper-Bill, Christopher; Vincent, Nicholas (eds.). Henry II: New Interpretations. The Boydell Press.
• Warren, W. L. (1995). Henry II. University of California Press.