VALENTINIAN III (Flavius Valentinianus Augustus), EMPEROR OF THE WESTERN ROMAN EMPIRE. — Son of the preceding emperor and of Galla Placidia, born in 419, died in Rome on 16 March 455.
At the death of his uncle Honorius (423), the Byzantine court, where Placidia had taken refuge with her son, sent Valentinian and his mother with an army to Italy to eliminate the usurper John; John was defeated and Valentinian was able to be crowned in Rome (425). He established his residence at Ravenna, and, given his tender age, effective government was in the hands of his mother. Placidia gave great impetus to the arts by embellishing the city with splendid monuments, and she benefited from the strong and brilliant work of the general Aetius to keep in check the barbarians pressing into Gaul and Spain. In 429 the Vandals landed in Africa, and, despite the agreement of 435, a few years later (439) they were masters of those regions and threatened Italy itself. In 451 Attila invaded Gaul but was defeated by Aetius at the Catalaunian Fields near Châlons; he came into Italy the following year, and Valentinian took refuge in Rome, from where he sent an embassy to the barbarian, which included Pope St Leo; Attila, who had already occupied and destroyed several cities, unexpectedly withdrew. Meanwhile in Rome, Valentinian, left alone as arbiter of government after his mother’s death (450), proved dissolute and incompetent, alienating everyone and especially the nobles whom he offended in their honour. A conspiracy led by Petronius Maximus, also to avenge the death of Aetius (September 454), eliminated him as he was on the Via Labicana.
The religious policy of Valentinian was directed towards increasingly repressing paganism, safeguarding the Catholic faith, and combating heretics. In 451 he prohibited, under penalty of death and confiscation of goods, the reopening of already closed temples or the offering of sacrifices (Cod. Iustin., I, 11, 7). Together with his mother and wife he wrote to Theodosius II urging proceedings against Eutyches (PL 54, 858 ff.), and in 452 he decreed that the memory of the patriarch Flavian should be rehabilitated (Cod. Iustin., I, 3, 23); in 451 he confirmed all privileges granted to the Catholic Church and abrogated contrary decrees (ibid., I, 2, 12). Decrees against heretics, especially the Nestorians, were issued in 428 and 435 (ibid., I, 1, 3; I, 5, 6); in 445 he issued a constitution against the Manicheans, by which they were declared enemies of the state, ordered to be expelled from the cities, forbidden to hold civil or military office, and deprived of all civil rights (PL 54, 622-24).