Aetius, c.396–454, Roman general. At first unfriendly to Valentinian III, he later made his peace with Valentinian's mother, Galla Placidia, and was given a command in Gaul. An ambitious general, he was embroiled in difficulties with his rival Boniface, who defeated him near Rimini in 432. Aetius went briefly into exile among the Huns but returned in 433 and rose to be the chief ruler of the Western Empire. He defeated the Germans in Gaul, then crowned his career by commanding (451) Roman and Visigothic troops in the repulse of Attila and the Huns in the battle near the modern Châlons-en-Champagne—a battle generally said to have saved the West. Valentinian, presumably jealous of Aetius' success, had him murdered.

Aetius (āē´shēəs), d. 367, Syrian theologian. He became prominent (c.350) as an exponent of the extreme Arianism developed mainly by his secretary Eunomius. Members of his party were called Aetians and Anomoeans.