CALIXTUS II  . (d . 1124), pope from II19 to 1I24, was Guido, a member of a noble Burgundian family, who became archbishop of Vienne about 1088, and belonged to the party which favoured reform in the Church . In September 1112, after Pope Paschal II. had made a surrender to the emperor Henry V., Guido called a council at Vienne, which declared against lay investiture, and excommunicated Henry . In February 1119 he was chosen pope at Cluny in succession to Gelasius II., and in opposition to the anti-pope Gregory VIII., who was in Rome . Soon after his consecration he opened negotiations with the emperor with a view to settling the dispute over investiture . Terms of peace were arranged, but at the last moment difficulties arose and the treaty was abandoned; and in October 1119 both emperor and anti-pope were excommunicated at a synod held at Reims . The journey of Calixtus to Rome early in 1120 was a triumphal march . He was received with great enthusiasm in the city, while Gregory, having fled to Sutri, was delivered into his hands and treated with great ignominy . Through the efforts of some German princes negotiations between pope and emperor were renewed, and the important Concordat of Worms made in September 1122 was the result . This treaty, made possible by concessions on either side, settled the investiture controversy, and was confirmed by the Lateran council of March 1123 . During his short reign Calixtus strengthened the authority of the papacy in southern Italy by military expeditions, and restored several buildings within the city of Rome .

During preparations for a crusade he died in Rome on the 13th or 14th of

December 1124 . See M . Maurer, Pabst Calixt H . (Munich, 1889); U . Robert, Histoire du ',ape Calixte H . (Paris, 1891) ; and A . Hauck's Realencyklopadie, Band iii . (Leipzig, 1897) .