Constantine (c.274–337), first Christian Roman emperor (306–37), known as ‘the Great’. Born at Naissus (now Nis), Constantine was the son of Constantius I by Helena. In 305 Constantius succeeded as Augustus (senior emperor) of the West. Constantine fled from the court of Galerius, eastern Augustus, in time to be at his father's death-bed at York in 306. He was illegally proclaimed Augustus by the army there. In 312 he invaded Italy and defeated Maxentius near Rome, apparently after a Christian vision. By 324 Constantine was sole Augustus. He was an energetic general and recast the Roman army. He also continued the administrative and fiscal reforms of Diocletian. Constantine promoted Christianity financially, legally, and theologically, being baptized on his death-bed in 337. He probably revisited Britain in 312 and 314, taking the title Britannicus in 315, and an edict of 319 is addressed to the Vicarius of the Britains, Pacatianus.

Alan Simon Esmonde Cleary

Constantine (c.274–337), Roman emperor; known as Constantine the Great. He was the first Roman emperor to be converted to Christianity and in 324 made Christianity a state religion, though paganism was also tolerated. In 330 he moved his capital from Rome to Byzantium, renaming it Constantinopolis (Constantinople). In the Orthodox Church he is venerated as a saint.