William FitzAlan (1105–1160) was a nobleman of Breton ancestry. He was a major landowner, a Marcher lord with large holdings in Shropshire, where he was the Lord of Oswestry, as well as in Norfolk and Sussex. He took the side of Empress Matilda during the Anarchy and underwent considerable hardship in the Angevin cause before regaining his lands and former status. William's younger brother, Walter fitz Alan (d. 1177), was to become 'the undoubted ancestor of the royal House of Stuart'.