Communist state, in popular usage, is a state with a form of government characterized by single-party rule or dominant-party rule of a communist party and a professed allegiance to a Leninist or Marxist–Leninist ideology as the guiding principle of the state. Technically, "communist state" is a contradictio in terminis as a communist society as defined by both Marxists and anarcho-communists is in principle stateless. From this perspective, the term Marxist-Leninist state is more appropriate.

Historically, a "communist state" referred to a system where public ownership of all or most means of production by the Communist party-run state is deemed necessary to further the interests of the working class; today, a communist state can also, for instance, refer to contemporary China and Vietnam, where a Communist Party-run state exists alongside a mixed economy. According to Marxist–Leninists, the state is a tool in the hands of the ruling class, which in a socialist society is the working class, so a socialist state is, according to Leninists, a state of the working class.