Sir Thomas FitzAlan (died 1430) of Betchworth Castle in Surrey was a medieval English knight.
He was born to John FitzAlan, 2nd Baron Arundel and Elizabeth le Despenser of Betchworth and was a grandson of John FitzAlan (D'Arundel) and Eleanor Maltravers, 2nd Baroness Maltravers (Mautravers).
Sir Thomas married Joan Moyns, and they were parents of Eleanor FitzAlan. She was married to Sir Thomas Browne. They had four sons and a daughter, and were ancestors of the poet, Percy Bysshe Shelley. Another descendant of theirs is the American Abolitionist, John Brown.
On the death of Thomas FitzAlan, Betchworth Castle passed from the FitzAlans to the Brownes, who occupied it until 1690.