Revolutionary socialism is a political philosophy, doctrine, and tradition within socialism that stresses the idea that a social revolution is necessary to bring about structural changes in society. More specifically, it is the view that revolution is a necessary precondition for transitioning from a capitalist to a socialist mode of production. Revolution is not necessarily defined as a violent insurrection; it is defined as a seizure of political power by mass movements of the working class so that the state is directly controlled or abolished by the working class as opposed to the capitalist class and its interests.

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.