William Fitz Alan was a Norman nobleman who lived in Oswestry and Clun near Shrewsbury, along the medieval Welsh Marches. William was the son of William Fitz Allan, controlling the castles of Clun and Oswestry and later became the High Sheriff of Shropshire. William married Mary de Lacy. When William came to inherit his lands in 1210, King John demanded a fee of 10,000 marks; unable to pay, William was unable to inherit. He only outlived his father by a few years, dying around Easter 1215. The estates were eventually reclaimed by his younger brother John Fitzalan.