A one-party state, single-party state, one-party system or single-party system is a governance structure in which only a single political party controls the ruling system. All other parties are either outlawed or only enjoy limited and controlled participation in elections. Sometimes the term "de facto one-party state" is used to describe a dominant-party system that, unlike the one-party state, allows democratic multiparty elections, but the existing practices or balance of political power effectively prevent the opposition from winning power.

Marxism–Leninism is a communist ideology that became the largest faction of the communist movement in the world in the years following the October Revolution. It was the predominant ideology of most communist governments throughout the 20th century. It was developed in Russia by Joseph Stalin and drew on elements of Bolshevism, orthodox Marxism, and Leninism. It was the state ideology of the Soviet Union, Soviet satellite states in the Eastern Bloc, and various countries in the Non-Aligned Movement and Third World during the Cold War, as well as the Communist International after Bolshevization.