Valentinian III

Valentinian III (Latin: Placidus Valentinianus; 2 July 419 – 16 March 455) was Roman emperor in the West from 425 to 455. Starting in childhood, his reign over the Roman Empire was one of the longest, but was dominated by civil wars among powerful generals and the barbarian invasions. He was the youngest sole emperor in the Western Roman Empire (aged 6).

He was the son of Galla Placidia and Constantius III, and as the great-grandson of Valentinian I (r. 364–375) he was the last emperor of the Valentinianic dynasty. As a grandson of Theodosius I (r. 379–395), Valentinian was also a member of the Theodosian dynasty, to which his wife, Licinia Eudoxia, also belonged. A year before assuming the rank of augustus, Valentinian was given the imperial rank of caesar by his half-cousin and co-emperor Theodosius II (r. 402–450). The augusta Galla Placidia had great influence during her son's rule, as did the military commander Flavius Aetius, who defended the western empire against Germanic and Hunnic invasions. Attila the Hun repeatedly menaced Valentinian's domains, being repulsed by a coalition under Aetius's leadership at the Battle of the Catalaunian Plains and calling off a subsequent invasion after negotiations led by Pope Leo I.

The emperor later fell out with Aetius and killed him. Valentinian was assassinated in turn by Aetius's bodyguards, ending a reign marked by the ongoing collapse of the western empire.