Callixtus III (born December 31, 1378, near Játiva, kingdom of Aragon [Spain]—died August 6, 1458, Rome [Italy]) was the pope from 1455 to 1458.
As a member of the Aragonese court, he reconciled King Alfonso V with Pope Martin V, who appointed Callixtus bishop of Valencia in 1429. Pope Eugenius IV made him a cardinal in 1444.
As a compromise between the influential Colonna and Orsini families of Rome, Borgia was chosen as pope on April 8, 1455, succeeding Pope Nicholas V. (He was thought unlikely to reign long, in view of his advanced age.) Callixtus made a Crusade to recover Constantinople (now Istanbul) from the Turks the first order of his pontificate, but he failed despite heroic efforts. He was successful, however, in raising a pontifical fleet that relieved many of the Aegean Islands.
The repulse of the Turks from Belgrade on August 6, 1456, was commemorated by Callixtus when he instituted the Feast of the Transfiguration (1457), ordering that it be observed on that day. His pontificate revised St. Joan of Arc’s trial by proclaiming her innocence. His personal life was blameless, but his nepotism was widely resented. Following the fashion of his time, he showered favours on his nephew Rodrigo Borgia, whom he made cardinal and generalissimo of the papal forces and who later became Pope Alexander VI (see also Borgia family). Callixtus was succeeded by Pope Pius II.