History › Classical age › Christianity
Constantine the Great
reigned 306–337; converted 312; Edict of Milan 313· Person· Europe
Well documentedSolid records, physical evidence or scientific consensus.
Roman emperor who was the first to embrace Christianity, legalized it, and founded Constantinople as a new capital.
See it on the History map →What happened
Proclaimed emperor by his troops at York, Britain, in 306, Constantine fought rivals for control. Before the Battle of the Milvian Bridge near Rome in 312, he reportedly saw a sign from the Christian God, and his soldiers marked their shields; he won. In 313 the Edict of Milan granted toleration to all religions. He funded churches, called the Council of Nicaea in 325, reunited the empire, and in 330 dedicated Constantinople. He was baptized on his deathbed in 337.
Why it matters
His support turned Christianity from a persecuted minority into the empire's favored faith, and his new capital anchored the eastern empire for over 1,100 years.
Legacy and how we know
A biography by Bishop Eusebius, who knew him, the writer Lactantius, his surviving laws and coins, and monuments like the Arch of Constantine in Rome.
Still debated
How sincere his conversion was, versus political calculation, is debated; his coins kept the pagan sun god for years afterward.
Connections (2)
▸Constantine the Great legalized and championed ChristianityWell documented
The connection
After his Milvian Bridge victory in 312, Constantine credited the Christian God. The Edict of Milan (313) ended persecution and returned confiscated church property. He gave churches money, land and legal privileges, built Old St. Peter's in Rome and the Church of the Holy Sepulchre in Jerusalem, and summoned the Council of Nicaea (325) to settle disputes over Christ's nature.
When and how
Rome, Milan and Nicaea (modern İznik, Turkey), 312–337; Constantine and some 250–300 bishops at Nicaea.
How we know
Eusebius' Life of Constantine, the edict's text preserved by Lactantius, his laws, and council records.
Debates and open questions
Whether his support came from genuine faith or politics, and how much imperial backing changed Christianity itself, are debated.
▸Constantine the Great founded the capital of Byzantine EmpireWell documented
The connection
Constantine rebuilt the old Greek town of Byzantium on the Bosporus strait as a 'New Rome', dedicating it in 330. Controlling the sea route between the Black Sea and the Mediterranean, and close to the rich eastern provinces and frontiers, it became the capital of the eastern empire for over 1,100 years. It is today's Istanbul.
When and how
Byzantium, on the Bosporus, 324–330; Constantine.
How we know
Contemporary writers, surviving monuments such as the Column of Constantine, and the name itself: Constantinople, 'Constantine's city'.
Debates and open questions
Whether he planned a Christian capital or a traditional Roman one is debated; the city also displayed many pagan statues.