High Quality Content by WIKIPEDIA articles! Pope Calixtus II (or Calistus II) (died December 13, 1124), born Guy de Vienne, the fourth son of William I, Count of Burgundy (1057–87), was elected Pope on February 1, 1119, after the death of Pope Gelasius II (1118–19). His pontificate was shaped by the Investiture Controversy, which he was able to settle through the Concordat of Worms (in 1122). Although his birth date is not known, his eldest brother was born in 1061, therefore we can assume that Guy de Vienne himself was born between 1065 and 1068.