Magnentius

Magnentius (c. 316–353) was a Roman general who became Western Roman Emperor from 350 to 353. He was likely of provincial (Gaulish) origin and rose through the ranks of the late-Constantinian army. In 350, following the assassination of Constans I, Magnentius seized power in Gaul and proclaimed himself emperor at Augustodunum (Autun). He quickly secured control of the western provinces, especially Gaul and Italy, and minted coins bearing his portrait with the title Augustus to solidify his legitimacy.

The usurpation precipitated a civil war with Constantius II, the eastern emperor. Magnentius defended his position against Constantius’ campaigns across the western provinces, with battles fought in Gaul and Italy. After several years of fighting, the balance of power shifted in favor of Constantius II. In 353, Magnentius was defeated at the Battle of Mons Seleucus; facing capture, he killed himself.

Magnentius’ brief usurpation is notable as one of the major civil conflicts of the Constantinian era. His revolt undermined central authority in the Western Roman Empire and contributed to the broader pattern of provincial military power challenging imperial legitimacy. The defeat and death of Magnentius restored control of the Western provinces to Constantius II and influenced subsequent dynastic and administrative arrangements in the late empire.