Callixtus I is elected as the sixteenth pope, although Hippolytus of Rome is soon thereafter elected as a rival pope.
Pope Callixtus I, also called Callistus I, was the bishop of Rome (according to Sextus Julius Africanus) from c. 218 to his death c. 222 or 223. He lived during the reigns of the Roman emperors Elagabalus and Alexander Severus. Eusebius and the Liberian catalogue gave him five years of episcopate (217–222). In 217, when Callixtus followed Zephyrinus as Bishop of Rome, he started to admit into the Church converts from sects or schisms. He was martyred for his Christian faith and is venerated as a saint by the Catholic Church (the patron saint of cemetery workers).