William I of Burgundy in the context of "Pope Callixtus II"

Pope Callixtus II or Callistus II (c. 1065 – 13 December 1124), born Guy of Burgundy, was the head of the Catholic Church and ruler of the Papal States from February 1119 to his death in 1124. His pontificate was shaped by the Investiture Controversy, which he was able to settle through the Concordat of Worms in 1122.

As son of Count William I of Burgundy, Guy was a member of and connected to the highest nobility in Europe. He became archbishop of Vienne and served as papal legate to France. He attended the Lateran Synod of 1112. He was elected pope at Cluny in 1119. The following year, prompted by attacks on Jews, he issued the bull Sicut Judaeis which forbade Christians, on pain of excommunication, from forcing Jews to convert, from harming them, from taking their property, from disturbing the celebration of their festivals, and from interfering with their cemeteries. In March 1123, Calixtus II convened the First Lateran Council which passed several disciplinary decrees, such as those against simony and concubinage among the clergy, and violators of the Truce of God.