By 380 CE Christianity was the official religion of?

By 380 CE, Christianity had been declared the official religion of the Roman Empire through the Edict of Thessalonica, issued by Emperor Theodosius I. This edict recognized Nicene Christianity as the state religion, promoting it above other religious practices. The move marked a significant shift in the Roman Empire, solidifying the influence of Christianity in politics and society and suppressing pagan and other religious practices.