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Constantine the Great
emperor 306–337; Milvian Bridge 312· Person· People
Historical recordConfirmed by archaeology, outside sources or contemporary records.
The first Christian Roman emperor, who legalized the faith, called the Council of Nicaea and founded Constantinople.
See it on the Bible & Christianity map →What it is
Proclaimed emperor by his troops at York in 306, Constantine fought rivals for the throne. Before the Battle of the Milvian Bridge outside Rome (October 28, 312) he reportedly saw a sign, the Chi-Rho (the first Greek letters of 'Christ'), and was told 'In this sign, conquer.' He won, legalized Christianity (313), funded churches like Old St Peter's, made Sunday a rest day (321), became sole emperor (324), and was baptized on his deathbed in 337.
Why it matters
He turned Christianity from a persecuted minority into the emperor's favored faith, binding church and state together in Europe for the next 1,400 years.
Life, legacy and sources
Eusebius's Life of Constantine and Lactantius describe the vision, in differing versions. The Arch of Constantine (315) and his coins, which kept sun-god imagery into the 320s, show a gradual shift.
Questions and debates
Historians debate how sincere or complete his conversion was; he had his son Crispus and wife Fausta executed in 326. Orthodox churches venerate him as a saint.
Inside this (4)
Connections (4)
▸Constantine the Great issued, with Licinius, Edict of Milan: tolerance for ChristiansHistorical record
The connection
Fresh from his Milvian Bridge victory, Constantine met Licinius, the eastern emperor, at Milan, where Licinius married Constantine's half-sister Constantia. They agreed on freedom of religion for Christians and all others and the return of church property. Licinius then defeated his eastern rival Maximinus Daia and published the policy in the East.
When and where
Milan, February 313; published by Licinius at Nicomedia on June 13, 313.
Historical evidence
The text survives in Lactantius (chapter 48) and in Eusebius's Church History (Book 10.5), both written within a few years of the event.
Questions and debates
Licinius's own motives are unclear: he was not a Christian, and the deal may have been mainly an alliance against Maximinus Daia, who had resumed persecuting Christians in the East.
▸Constantine the Great called Council of NicaeaHistorical record
The connection
Becoming sole emperor in 324, Constantine found the eastern church split over Arius. He sent Bishop Hosius of Córdoba to mediate, then summoned bishops to Nicaea, near his palace, at state expense. He opened the council in person, reportedly backed the word homoousios, and exiled those who refused to sign, setting the pattern of emperors calling councils.
When and where
Nicaea in Bithynia (İznik, Turkey), May–July 325; the meeting was first planned for Ancyra (Ankara).
Historical evidence
Eusebius of Caesarea, an eyewitness, describes it in his Life of Constantine and in a letter to his home church; several of Constantine's letters survive.
Questions and debates
Whether Constantine cared about theology or only unity is debated; he later recalled Arius and was baptized by an Arian-leaning bishop.
▸Constantine the Great founded Constantinople, the 'New Rome'Historical record
The connection
After defeating Licinius nearby at Chrysopolis in 324, Constantine picked Byzantium for a new capital on the Bosporus, controlling the route between Europe and Asia and closer to his frontiers. He rebuilt it on a grand scale, with a senate, forum and the Church of the Holy Apostles, where he was buried, and dedicated it in 330.
When and where
Byzantium on the Bosporus, 324–330; dedicated on May 11, 330.
Historical evidence
Eusebius and the pagan historian Zosimus describe the founding; the Column of Constantine (Çemberlitaş) still stands in Istanbul.
Questions and debates
How the site was chosen is debated: the church historian Sozomen says Constantine first began building near ancient Troy until a dream sent him elsewhere.
▸Constantine the Great built the Holy Sepulchre church in Jerusalem, City of DavidHistorical record
The connection
After legalizing Christianity, Constantine had a temple of Venus torn down from the site Christians remembered as Jesus' tomb and built the Church of the Holy Sepulchre over it. With his mother Helena's pilgrimage, this made Jerusalem a Christian holy city and pilgrimage center.
When and where
Jerusalem, begun about AD 326, after the Council of Nicaea, and dedicated in 335; Bishop Macarius of Jerusalem oversaw the project.
Historical evidence
Eusebius, Constantine's contemporary, describes the building in his Life of Constantine and quotes the emperor's letter to Macarius ordering it.
Questions and debates
Whether the church covers Jesus' actual tomb is debated; many archaeologists think it plausible, since the site lay outside the walls then. Helena finding the True Cross is legend.