William de Percy, 6th Baron Percy  William de Percy (died 1245), sixth feudal baron of Topcliffe, was an English noble. He was a son of Henry de Percy and Isabel de Brus. 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.