Louis I, also known as Louis the Great (Hungarian: Nagy Lajos; Croatian: Ludovik Veliki; Slovak: Ľudovít Veľký) or Louis the Hungarian (Polish: Ludwik Węgierski; 5 March 1326 – 10 September 1382), was King of Hungary and Croatia from 1342 and King of Poland from 1370 until his death in 1382. 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 Duke of Transylvania between 1339 and 1342 but did not administer the province.
Louis was of age when he succeeded his father in 1342, but his deeply religious mother exerted a powerful influence on him. He inherited a centralized kingdom and a rich treasury from his father. During the first years of his reign, Louis launched a crusade against the Lithuanians and restored royal power in Croatia; his troops defeated a Tatar army, expanding his authority towards the Black Sea. When his brother, Andrew, Duke of Calabria, husband of Queen Joanna I of Naples, was assassinated in 1345, Louis accused the queen of his murder and punishing her became the principal goal of his foreign policy. He launched two campaigns to the Kingdom of Naples between 1347 and 1350. His troops occupied large territories on both occasions, and Louis adopted the styles of Neapolitan sovereigns (including the title of King of Sicily and Jerusalem), but the Holy See never recognized his claim. Louis's arbitrary acts and atrocities committed by his mercenaries made his rule unpopular in Southern Italy. He withdrew all his troops from the Kingdom of Naples in 1351.
