An autocracy is a system of government in which a supreme political power is concentrated in the hands of one person, whose decisions are subject to neither external legal restraints nor regularized mechanisms of popular control (except perhaps for the implicit threat of coup d'état or mass insurrection).

Autocracy is any form of government in which one person is the supreme power within the state. It is derived from the Greek αὐτοκρατία: αὐτός ("self") and κρατεῖν ("rule"), and may be translated as "one who rules by himself". It is distinct from oligarchy ("rule by the few") and democracy ("rule by the people"). Like "despot", "tyrant", "strongman" and "dictator", "autocrat" has become a loaded word with a negative value judgment in contemporary English usage.

The term autokratōr was employed in antiquity to translate the Latin imperator into Greek. It was the primary word used by grecophones to refer to the Roman Emperor during the later Roman Empire through the seventh century CE and continued to be used in the Byzantine period, although it lost favor to Sebastos ("augustus") and Basileus (obscure: prob. "chieftain;" later "king") as synonyms for "emperor".^{[citation needed]} This use remains current in the modern Greek language, where the term is used for anyone holding the title "emperor," regardless of the actual power of the monarch.