Callixtus II, born Guy of Burgundy around 1065, was a Benedictine monk who served as the head of the Catholic Church from 1119 until his death in 1124. Before his election as pope at Cluny, he was the archbishop of Vienne and a papal legate in France. He is most recognized for his role in resolving the Investiture Controversy, a long-standing conflict between the papacy and the Holy Roman Empire, through the landmark Concordat of Worms in 1122.