Valerian,(190?–260), a Roman emperor. He was a general before becoming emperor in 253. At this time the Roman Empire was under attack by barbarians in the west and Persians in the east. Valerian named his son Gallienus, co-emperor and entrusted him with the defense of the west. Valerian took command of the Roman legions in the east. The Persians captured Valerian in 260, and shortly afterward killed him.