Louis I, also Louis the Great (; ; ) or Louis the Hungarian (; 5 March 132610 September 1382), was King of Hungary and Croatia from 1342 and King of Poland from 1370. He was the first child of Charles I of Hungary and his wife, Elizabeth of Poland, to survive infancy. A 1338 treaty between his father and Casimir III of Poland, Louis's maternal uncle, confirmed Louis's right to inherit the Kingdom of Poland if his uncle died without a son. In exchange, Louis was obliged to assist his uncle to reoccupy the lands that Poland had lost in previous decades. He bore the title of Duke of Transylvania between 1339 and 1342 but did not administer the province.