Basilius of Ancyra ( Βασίλειος , also called Basilas , Socr. ii. 42), a native of Ancyra, originally a physician (Hieron. de Vir. Ill. 89; Suidas, s.v. ), and subsequently bp. of that city, a.d.336-360, one of the most respectable prelates of the semi-Arian party, whose essential orthodoxy was acknowledged by Athanasius himself, the differences between them being regarded as those of language only (Athan. de Synod. tom. i. pp. 915, 619, ed. Morell, Paris, 1627). He was a man of learning, of intellectual power, and dialectical skill, and maintained an unwavering consistency which drew upon him the hostility of the shifty Acacians and their time-serving leader. The jealousy of Acacius was also excited by the unbounded influence Basil at one time exercised over the weak mind of Constantius, and his untiring animosity worked Basil's overthrow. On the deposition of Marcellus, the aged bp. of Ancyra, by the Eusebian party, on the charge of Sabellianism, at a synod meeting at Constantinople, a.d.336, Basil was chosen bishop in his room. He enjoyed the see undisturbed for eleven years; but in 347, the council of Sardica, after the withdrawal of the Eusebians to Philippopolis, reinstated Marcellus, and excommunicated Basil as "a wolf who had invaded the fold" (Socr. ii. 20). Three years later, a.d.350, the Eusebians were again in the ascendant, through the powerful patronage of Constantius, and Basil was replaced in his see by the express order of the emperor (Socr. ii. 26). Basil speedily obtained a strong hold over Constantius, who consulted him on all ecclesiastical matters, and did nothing without his cognizance. He and George of Laodicea were now the recognized leaders of the semi-Arian party (Epiph. Haer. lxxiii. 1). The next year, a.d.351, Basil took the chief part in the proceedings of the council that met at Sirmium, where Constantius was residing, to depose Photinus the pupil of Marcellus, who was developing his master's views into direct Sabellianism ( ib. lxxi. lxxiii.; Socr. ii. 30). Shortly after this we find him attacking with equal vigour a heresy of an exactly opposite character, disputing with Aetius, the Anomoean, in conjunction with Eustathius of Sebaste, another leader of the semi-Arian party. The issue of the controversy is variously reported, according to the proclivities of the historians. Philostorgius ( H. E. iii. 16) asserts that Basil and Eustathius were worsted by their antagonist; orthodox writers assign them the victory (Greg. Nys. in Eunom. lib. i. pp. 289, 296). Basil's representations of the abominable character of Aetius's doctrines so exasperated Gallus against him that he issued an order for his execution; but on having personal intercourse with him pronounced him maligned, and took him as his theological tutor. [See Aetius.] Basil's influence increased, and just before Easter, a.d.358, when a number of bishops had assembled at Ancyra for the dedication of a new church that Basil had built, Basil received letters from George of Laodicea speaking with great alarm of the spread of Anomoean doctrines, and entreating him to avail himself of the opportunity to obtain a synodical condemnation of Aetius and Eunomius. Other bishops were accordingly summoned, and eighteen anathemas were drawn up. Basil himself, with Eustathius and Eleusius, were deputed to communicate these anathemas to Constantius at Sirmium. The deputies were received with much consideration by the emperor, who ratified their synodical decrees and gave his authority for their publication. Basil availed himself of his influence over Constantius to induce him to summon a general council for the final settlement of the questions that had been so long distracting the church. It was ultimately decided to divide the council into two, and Ariminum was selected for the West, and Seleucia in Isauria for the East. The Eastern council met, Sept. 27, 359. Basil did not arrive till the third day. He was soon made aware that his influence with the emperor had been undermined by his Acacian rivals, and that his power was gone. When he reproved Constantius for unduly favouring them, the emperor bid him hold his peace, and charged him with being himself the cause of the dissensions that were agitating the church (Theod. ii. 27). At another synod convened at Constantinople under the immediate superintendence of Constantius, Acacius found himself master of the situation and deposed whom he would. Basil was one of the first to fall. No doctrinal errors were charged against him. He was condemned on frivolous and unproved grounds, together with Cyril of Jerusalem, Eustathius of Sebaste, and other leading prelates. Banishment followed deposition. Basil was exiled to Illyria (Soz. iv. 24; Philost. v. 1). On the accession of Jovian, a.d.363, he joined the other deposed bishops in petitioning that emperor to expel the Anomoeans and restore the rightful bishops; but Basil seems to have died in exile (Socr. iii. 25).
Athanasius speaks of his having written περὶ πίστεως (Athan. de Synod. u.s. ). Ittigius (de Haer. p. 453) defends him from the charge of Arianism. Jerome identifies him, but unjustly, with the Macedonian party (Tillemont, vol. vi. passim ).