a Roman soldier and statesman, a native of the province of Moesia.
He was an experienced soldier and officer when he was asked by Constantina, the sister of Roman Emperor Constantius II, to proclaim himself Caesar. Her brother Constans had been killed by Magnentius earlier that year and she probably thought Vetranio could protect her family and herself against the usurper. Vetranio accepted, and coins were minted in his name, showing the title of Augustus , rather than Caesar. Constantius first seemed to accept the new Emperor and his regalia and sent him money to raise an army. Vetranio frequently asked Constantius for money and military aid to fight Magnentius; he also sent letters to the emperor professing his loyalty to him. When negotiations deadlocked, Magnentius and Vetranio made an alliance; they sent an embassy to the emperor. The ambassadors met with the emperor in Heraclea in Thrace. Magnentius offered to marry his daughter to Constantius and to marry Constantia, the emperor's sister, in turn. But first, they required that the emperor lay down his arms and accept the honor as senior emperor. Constantius rejected their offer