EUDOXIUS. - One of the principal leaders of Arianism in the 4th century, bishop of Constantinople from 360 to 370. Born at Arabissus in Little Armenia, he listened to the lectures of St. Martyr Lucian (d. 312) at Antioch, and later turned to Arianism. As bishop of Germanicia, he took part in the Synod of the Dedication, held in 341. He was also present at most of the numerous synods convened by Constantius: at Serdica in 343 among the Easterners; probably at Sirmium in 351; certainly at Milan in 355 and at Sirmium in 357. From this city, upon hearing of the death of Leontius, the Arian bishop of Antioch, he hurried thither to secure the succession. He succeeded by violating the canons despite the protests of the electors. From that moment he openly declared himself for rigid Arianism, or Anomoeanism, represented by Aetius and Eunomius. But he soon found himself in difficulty, since the Emperor Constantius had declared for the semi-Arianism and Homoiousianism of Basil of Ancyra after the Council of Ancyra in 358. Facing the risk of exile and deposition, he temporarily left Antioch. But he soon had his revenge alongside Aetius of Caesarea, with whom he contributed to the triumph of the formula of Kiminium-Constantinople, i.e., of Homoianism, which became the official Arianism. Constantius rewarded his doctrinal compliance by transferring him to the see of Constantinople (360), which he held until his death (370). He managed to retain this position thanks to the protection of the Arian Emperor Valens, whom he himself had baptized before the campaign against the Goths (366-67).
E. was an ambitious man without character or firm convictions. The Arian Philostorgius describes him as a pleasant man of irreproachable conduct, but timid to the point of cowardice. Of his writings, which seem to have been numerous, only fragments of doubtful authenticity and a brief profession of faith survive, taken from a treatise on the Incarnation: *Athens about sarkōseōs* (cf. P. Caspari, *Alte und neue Quellen zur Geschichte des Taufsymbols und der Glaubensregel*, Christiania 1879, pp. 170-85).