known as Constantine the Great officially Flavius Valerius Constantinus
born Feb. 27, after AD 280?, Naissus, Moesia
died May 22, 337, Ancyrona, near Nicomedia, Bithynia
First Roman emperor to profess Christianity.
The eldest son of Constantius I Chlorus , he spent his youth at the court of Diocletian . Passed over as successor to the throne, he fought to make himself emperor. Victory at the Milvian Bridge outside Rome (312) made him emperor in the West; according to legend, a cross and the words in hoc signo vinces ("In this sign, conquer") appeared to him there and he forthwith adopted Christianity. In 313 he issued, with Licinius , the Edict of Milan, granting tolerance to Christians; he also gave land for churches and granted the church special privileges. He opposed heresies, notably Donatism and Arianism , and he convoked the important Council of Nicaea . After defeating and executing Licinius, he gained control of the East and became sole emperor. He moved the capital from Rome to Byzantium, which he renamed Constantinople (324). In 326 he had his wife and eldest son killed for reasons that remain obscure. He angered the Romans by refusing to participate in a pagan rite and never entered Rome again. Under his patronage, Christianity began its growth into a world religion. Constantine is revered as a saint in the Orthodox church.