The Principate is the term used to describe the earlier of the two phases of government in the ancient Roman Empire prior to its collapse in 476. Under the Principate, the reality of autocratic rule by the Emperor was masked by the forms and conventions of oligarchic self-rule from the period of the Roman Republic (509 BC-27 BC).

The term derives from the Latin word princeps, meaning chief or first, the title adopted by Caesar Augustus (r. 27 BC-AD 14), the first Emperor. After the Crisis of the Third Century almost resulted in the Empire's political collapse, the Emperor Diocletian replaced the Principate with the Dominate, in which the pretense of the old Republican forms was largely done away with.