340

Roman Empire

 * , capital of Emperor, becomes the largest city of the world, taking the lead from , capital of Emperor.
 * attacks his brother Constans near, aiming for sole control of the western half of the Empire, but is defeated.
 * Constans and Constantius II split the Empire between them.

Religion

 * succeeds as  in the  of.

Births

 * , church father (approximate date)
 * , translator (approximate date)
 * , politician and (approximate date)

Deaths

 * , joint emperor of the (killed in battle)
 * Saint