William de Warenne

William de Warenne (1256–1286) was the only son of John de Warenne, 6th Earl of Surrey, and Alice de Lusignan, half-sister of King Henry III. He married Joan, daughter of Robert de Vere, 5th Earl of Oxford, who bore him a son, John, later 7th Earl of Surrey, and a daughter Alice.

In 1286 William was killed in a tournament at Croydon, predeceasing his father, and it was later suggested that his enemies had planned his death as murder.