15th Pope of the Catholic Church, he reigned from 199 to 217. His pontificate was marked by the defense of orthodoxy against Montanist, Docetic, and Adoptionist heresies, and by the appointment of Callixtus as archdeacon, who would succeed him.
Saint Zephyrinus was the fifteenth Bishop of Rome, holding the papal see from 199 to 217. A native of Rome, his pontificate occurred during the reign of Emperor Septimius Severus, a difficult period for Christians despite the end of widespread persecution. He is best known for his defense of the orthodox doctrine of the Trinity and the divinity of Christ against various heresies then spreading, notably Montanism, Docetism, and the Adoptionism of Theodotus of Byzantium. He was criticized by Hippolytus of Rome for what Hippolytus considered excessive leniency and a lack of doctrinal clarity, especially towards the Monarchians. He appointed the future Pope Callixtus I as archdeacon, entrusting him with the administration of the Roman clergy and the management of the catacombs.