Marsala Cathedral (Italian - duomo di San Tommaso di Canterbury) is the largest church in the town of Marsala, Sicily and the Diocese of Mazara del Vallo. Its facade faces onto piazza della Repubblica and the nearby via Giuseppe Garibaldi. It is dedicated to the Anglo-Norman saint Thomas Becket, whose cult was introduced to Sicily via its close relations with England under William I and William II - the latter even married Henry II of England's daughter Joan, who also supported Thomas' cult despite Henry's part in triggering his death.