Constantine the Great (27 Feb c. 272/273 – 22 May 337). Constantine was born in Naissus, Moesia Superior (modern-day Serbia). His original name was Flavius Valerius Constantinus and his father was an officer in the Roman army. Constantine was Roman Emperor (A.D. 306-337). He was the first Roman Emperor to convert to Christianity and played a crucial role in the spread of the religion. With co-Emperor Licinius, he issued the Edict of Milan in 313, which proclaimed tolerance of all religions throughout the empire.