君士坦丁一世(280?年以後～337年)
Constantine I，亦称君士坦丁大帝（Constantine the Great）。
正式名称名为Flavius Valerius Contantinus。
第一位承认基督教的罗马皇帝。身为君士坦提乌斯一世的长子，他在戴克里先的宫廷度过幼年。他被忽略为王位继承人，而靠自己努力成为皇帝。在罗马城外米尔维安桥战役（312）的胜利使他成为西方的皇帝。根据传说，他见到那里出现一座十字架和「靠此神蹟，你将征服」的文字，此後即承认基督教。313年他与李锡尼发出「米兰敕令」，同意容忍基督教徒；他也把土地赠与教会，又给教会特权。他反对异端，特别是多纳图斯主义和阿里乌主义，还召开重要的尼西亚会议。在打败并处决李锡尼後，他控制了东方，成为唯一的皇帝。他把首都从罗马迁至拜占庭，并将之改名为君士坦丁堡（324）。326年他因不明的原因把妻子和长子处死。他拒绝参与世俗仪式而激怒了罗马人，此後未再踏进罗马一步。在他的赞助之下，基督教开始成长为世界性的宗教。君士坦丁在天主教会被尊为圣徒。
English version：
280?年以後～337年
Constantine I
officiallyFlavius Valerius ContantinusFirst 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 (“By this sign thou shalt 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 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 the site of 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.