Confessor Pope Sixtus III

Sixtus III, also known in Latin as Xystus III, was Bishop of Rome from 31 July 432 until his death in 440. The Liber Pontificalis describes him as a Roman by birth, the son of a man likewise named Xystus. No contemporary source records the year of his birth, and later guesses about his age at election are not historically grounded. Before becoming pope he was a well-known priest of the Roman church. A priest Sixtus, generally identified with the future pontiff, received a letter from Augustine of Hippo around 418 praising his opposition to Pelagianism after an earlier period in which his position had seemed less clear. He succeeded Pope Celestine I during the reigns of the Western emperor Valentinian III and the Eastern emperor Theodosius II.

The central doctrinal setting of his pontificate was the aftermath of the Council of Ephesus of 431, which had condemned Nestorius and affirmed Mary as Theotokos, Mother of God. Sixtus III confirmed the conciliar decrees and worked to heal the breach between Cyril of Alexandria and John of Antioch that had followed the council. The reunion of 433, expressed in a shared formula of faith, received his approval. He maintained Rome’s rejection of Pelagianism and refused attempts by Julian of Eclanum to obtain restoration. In questions of church order he defended the traditional papal vicariate over Illyricum, exercised through the bishop of Thessalonica, against moves associated with the court of Constantinople to draw those provinces toward the Eastern capital.

Sixtus III is especially remembered for a substantial building and decoration program in Rome. After Ephesus he rebuilt and adorned the Esquiline basilica now known as Santa Maria Maggiore, dedicating it to the Mother of God; mosaics of his time survive on the triumphal arch, together with the inscription recording that Xystus the bishop offered the work to the people of God. He reconstructed the Lateran baptistery on an octagonal plan and furnished it with verse inscriptions on baptism. He also enlarged the shrine complex of Saint Lawrence on the Via Tiburtina, adding a new basilica beside the earlier church at the martyr’s tomb. These projects tied Roman liturgical life to the Christological and Marian teaching of Ephesus.

He died in Rome on 18 August 440 and was buried in the crypt of the basilica of Saint Lawrence outside the walls, on the Via Tiburtina. Leo I, later called Leo the Great, succeeded him. Sixtus III was venerated as a saint and confessor rather than as a martyr. His name entered the ancient Roman tradition of cult; there is no record of a later formal canonization of the medieval type. The Roman Martyrology commemorates him on 28 March.