Centuries: 3rd century - 4th century - 5th century
- January 2, Alamanni cross frozen Rhine in large numbers, invading Roman Empire
- October 1 - Pope Damasus I becomes Bishop of Rome. Romans unhappy with this choice elect the antipope Ursicinus.
- Valens defeats the troops of Procopius in the Battle of Thyatria, bringing an end to his revolt.
- Athanasius returns from exile.