Casimir III the Great reigned as the King of Poland from 1333 to 1370. He also later became King of Ruthenia in 1340, and fought to retain the title in the Galicia-Volhynia Wars. He was the last Polish king from the Piast dynasty.

Louis I, also Louis the Great or Louis the Hungarian, 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.