Calixtus II (or Calistus II) (died 13 December 1124), born Guy de Burgundy, the fourth son of William I, Count of Burgundy, was elected Pope on 1 February 1119 after the death of Pope Gelasius II. His pontificate was shaped by the Investiture Controversy, which he was able to settle through the Concordat of Worms (in 1122).