Sir William Weston (c. 1470 – 7 May 1540) was the last Prior of the Order of Knights of the Hospital of Saint John of Jerusalem in England before the Dissolution of the Monasteries, during the reign of King Henry VIII.
His brother was Sir Richard Weston (1465–1541) of Sutton Place in Surrey, a courtier of King Henry VIII and a diplomat who served as Governor of Guernsey, Treasurer of Calais and Under-Treasurer of the Exchequer.
He was also placed in command of a ship in the Navy of the Order of Saint John known as the Great Carrack (Santa Anna), "the first iron-clad recorded in history...sheathed with metal and perfectly cannon-proof (with) room for five hundred men, and provisions for six months".
There was some difficulty over the appointment and a rumour was current that the King Henry intended, after having conferred the office on a favourite, to separate the English knights from the rest of the order, and to station them at Calais, his personal possession.
The matter was settled by a personal visit to him of Grand Master Philippe Villiers de L'Isle-Adam, the heroic defender of Rhodes, following which Henry assented to the appointment of Sir William Weston and withdrew his first claim for a yearly tribute of £4,000 from the new Prior.