Auxentius of Milan (fl. c. 355; died 374), by tradition a Scythian of Cappadocia, was an Arian theologian of some eminence who held the see of Milan. Ambrose praised him for his skills in rhetoric, though he considered him "worse than a Jew". He is not to be confused with Saint Auxentius of Mopsuestia (d. 360) an early Christian martyr and an Eastern Orthodox and Roman Catholic saint, or with Saint Auxentius, a hermit cleared of heresy at the Council of Chalcedon and an Eastern Orthodox and Roman Catholic saint.
When Constantius II deposed the orthodox bishops who resisted, Auxentius, favored by the empress Justina, was installed in the see of Dionysius and came to be regarded as the great opponent of the Nicene doctrine in the West. So prominent did he become, that he was specially mentioned by name in the condemnatory decree of the synod (369) which Damasus, bishop of Rome, urged by Athanasius, convened in defence of the Nicene doctrine.
The chief source of information about him is the Liber contra Auxentium in the Benedictine edition of the works of Hilary.