Gaius Galerius (Gaius Galerius Valerius Maximianus Augustus), emperor of Rome, dies at about the age of 50.
Galerius was the primary motivation behind Emperor Diocletian beginning the persecution of Christians — persecutions that come to be named after Diocletian rather than Galerius. Diocletian had not been especially anti-Christian in his policies, though he wasn't especially friendly towards them either. When he and Galerius go to the oracle of Apollo at Didyma for advice, they are told that Apollo can't give them advice because of the presence of the impious on Earth.
The "impious" are identified as the Christians, so Diocletian agrees to Galerius' demand that the Roman state begin a general persecution of them.
Eventually Galerius relents in his hatred of Christians, though only on his deathbed. He only goes so far as to end the killing of Christians for what they believe. Christians are still admonished to pray for the leaders of the Roman government.