William II (William the Good), c.1153–1189, king of Sicily (1166–89), son and successor of William I. He married (1177) Joan, daughter of Henry II of England. As an ally of Pope Alexander III and the Lombard League, he was at war with Holy Roman Emperor Frederick I, but in 1184 he made peace in order to resume the attempts of his grandfather, Roger II, to conquer the Byzantine Empire. He took Durazzo and Salonica, but was defeated (1185) by Isaac II. When he died childless, his kingdom was claimed by his aunt Constance, whom he had designated as his successor, but the crown went instead to his cousin Tancred of Lecce.