Calixtus, the name of three popes. I. The first, born in slavery, was bishop of Rome from about 217 to 223, when he is said to have suffered martyrdom. II. Gnido of Burgundy, born near Besancon, died in Rome in 1124. He was the fifth son of William, count of Burgundy, and related to the queen of France, the emperor of Germany, and the king of England. In 1096 he was archbishop of Vienne, and he soon after went to the courts of France and England as papal legate, principally in order to settle the vexed question of lay investiture. In 1119 he was elected to succeed Pope Gela-sius II. He held councils at Toulouse and at Rheims, at the latter of which the emperor Henry V., while encamped in the vicinity with 30,000 men, was solemnly excommunicated by Calixtus, in presence of the council. After closing the council Calixtus went to Rome in 1120, where an antipope, named Gregory VIII., had established himself under the protection of the emperor; but Calixtus expelled him, and with the aid of the neighboring princes stormed the castle of Sutri, whither he had fled, and made him prisoner. He next attacked the Frangipani and Cenci, broke their power, and demolished their castles.

In 1121 and 1122 he sent legates to Germany; a diet was held at Wurzburg, and finally the pactum Ca-lixtinum, or concordat of Worms, was concluded. Henry sent ambassadors to the pope, and in 1123 the first Lateran council was held, at which 300 bishops were present, and in this council Henry was absolved, and the question of investiture finally settled. In the remainder of his life Calixtus paid particular attention to the decoration of St. Peter's church, and repairing the aqueducts of Rome. III. Alfonso Borgia, a member of the Spanish branch of the Borgia family, born at Valencia about 1380, died Aug. 6, 1458. After having received an excellent education, he was promoted to a canonry by the antipope Benedict XIII. (Pedro de Luna), whose party was embraced by Alfonso V., king of Aragon. Having soon after been called to the royal council by Alfonso, he was sent by him to Benedict's successor, in order to induce him to abandon his pretensions; and having succeeded in this mission, he negotiated the reconciliation of his sovereign with Pope Martin V., and was rewarded by that pontiff with the archbishopric of Valencia. In 1444 he was made cardinal by Eugenius IV., as a reward for negotiating a reconciliation between himself and Alfonso V. On April 8, 1455, he succeeded Nicholas V. on the papal throne.

The ruling idea of his pontificate was the revival of the crusades against the Turks, who had just captured Constantinople. He endeavored vainly to unite all Christendom in this undertaking. The greatest fault which he committed was the elevation of his two unworthy nephews, Rodrigo Lenzuolo (who assumed the name of Borgia) and Milo, to the dignity of cardinals, the former of whom became afterward pope under the name of Alexander VI.