The Dominate, also known as the late Roman Empire, is the despotic form of imperial government of the late Roman Empire. It followed the earlier period known as the Principate. Until the empire was reunited in 313, this phase is more often called the Tetrarchy.

The Crisis of the Third Century, also known as the Military Anarchy or the Imperial Crisis (235–285), was a period in Roman history during which the Roman Empire had nearly collapsed under the combined pressure of repeated foreign invasions, civil wars and economic disintegration. At the height of the crisis, the Roman state had split into three distinct and competing polities.