1. Arian bishop of Milan, A.D. 355-374 (Sozomen, Hist. Eccl. 6, 23). He was the leader of the Arians in the Western churches. When the orthodox bishops, at a provincial, synod held in 369, under the presidency of Bishop Damasus of Rome, condemned Arianism, they did not dare to pronounce the anathema against Auxentius, because they knew him to be protected by the favor of the Emperor Valentinian I. Although they were at last prevailed upon by Athanasius to mention in their synodal epistle to the Illyrians the condemnation of Auxentius, the latter maintained himself in his see until his death. He was succeeded by Ambrose (q.v.).
2. Abbot, born in Syria, being the son of Abdus, who was compelled by the persecution under King Sapor to leave his country and settle in Syria. In 432 Auxentius came to Constantinople, where he received an appointment in the royal guards, but afterward retired to a solitary mountain in Bithynia, named Oxius, where, clothed only in the skins of animals, he led a life of the most complete austerity. When the Council of Chalcedon was convoked, Auxentius was unwillingly compelled to attend, and subscribed the decrees. After this he retired to a more remote mountain, called Siope, where multitudes of persons flocked to hear him. Of these, many continued to abide near him in cells, and followed the example of his ascetic course of life. He died in 470. His memory is celebrated on the 14th of February. — Sozomen, Hist. Eccl. 7, 21; Butler, Lives of Saints, Feb. 14; Landon, Eccl. Dict. s.v.