Constantine the Great
Constantine the Great (AD 280-337), Roman emperor, who established Christianity as the official imperial religion. He succeeded his father, Constantius Chlorus, as emperor of the West in 306; after defeating all his rivals in a series of civil wars, he became sole emperor in 325. In 313, having seen a heavenly vision of the cross before a battle, Constantine was converted to Christianity. From then on he favoured Christians and became increasingly severe towards pagans. He founded Constantinople, formerly Byzantium, as the capital of the Christian empire (324).