Edict of Thessalonica

The Edict of Thessalonica, issued in 380 AD by Emperor Theodosius I, declared Christianity the official state religion of the Roman Empire. It mandated that all Roman subjects adhere to Nicene Christianity, the orthodox Christian belief, and recognized it as the only legitimate faith. This edict effectively marginalized other religious practices, especially paganism and heretical Christian groups, and helped unify religious practice across the empire under Christianity. It marked a significant moment in the Christianization of the Roman Empire, shaping its religious landscape for centuries to come.