Vetranio (d. c. 360), born in the province of Moesia in a part of the region located in modern Serbia, is sometimes but incorrectly referred to as Vetriano. He was an experienced soldier and officer when he was asked by Constantina, the sister of Roman Emperor Constantius II, to proclaim himself Caesar (March 1, 350). 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 (full emperor), rather than Caesar. Constantius first seemed to accept the new Emperor and sent him money to raise an army, as well as his regalia.

Constantius, who was on a campaign against the Persians when Magnentius came to power, returned to the West and met with Vetranio. Vetranio subsequently abdicated on December 25, 350. He was allowed to live the remainder of his years as a private citizen on a state pension in Prusa ad Olympium, Bithynia.