William de Percy (died 1245), sixth feudal baron of Topcliffe, was an English noble.
His father Henry de Percy was a son of Joscelin of Louvain and Agnes de Percy, while his mother Isabel de Brus was the daughter of Adam II de Brus, 3rd Lord of Skelton and great-granddaughter of Robert de Brus, 1st Lord of Annandale, belonging to an English branch of the same family that yielded Clan Bruce of Scotland. He died in 1245 and was buried at Sawley Abbey.
He married firstly married Joan, daughter of William de Briwere and Beatrice de Vaux. They are known to have had the following known issue.
William married secondly Ellen, daughter of Ingram de Balliol and Agnes de Berkeley, they are known to have had the following known issue.