The Edict of Milan was the 313 CE Roman decree that granted religious toleration to Christians throughout the empire.
The policy was agreed by Constantine I and Licinius at meetings in Mediolanum, the city now called Milan. It ended official persecution and allowed Christians to worship openly. The agreement also ordered the return of confiscated Christian property, including meeting places and cemeteries.
The Edict of Milan did not make Christianity the Roman Empire’s official religion. That later development is associated with the Edict of Thessalonica, issued by Theodosius I and his colleagues in 380 CE. The earlier decree instead established a broad policy of religious freedom for Christians and other religious groups.
Constantine later became Christianity’s most important imperial patron, while Licinius eventually fought Constantine and was defeated in 324 CE. Their agreement therefore became a major turning point in Roman religious history.