Centuries: 2nd century - 3rd century - 4th century
- March 1 - Diocletian and Maximian appoint Constantius Chlorus and Galerius as Caesars. This is considered the beginning of the Tetrarchy.
- Probus succeeds Rufinus as Patriarch of Constantinople
- Sassanid Shah Bahram III succeeds Bahram II.
- Sassanid Shah Narseh succeeds Bahram III.
- Tuoba Fu succeeds Tuoba Chuo as chieftain of the Chinese Tuoba tribe.
- Allectus usurps power in Gaul after assassinating Carausius.