Socialist democracy is a political system that aligns with principles of both socialism and democracy. It includes ideologies such as council communism, social democracy, democratic socialism, and soviet democracy, as well as Marxist democracy like the dictatorship of the proletariat. It was embodied in the Soviet system (1922–1991). It can also denote a system of political party organization like democratic centralism, or a form of democracy espoused by Marxist–Leninist political parties or groups that support one-party states. The Socialist Federal Republic of Yugoslavia (1945–1992) styled itself a socialist democracy, as did the People's Republic of Bulgaria (1946–1990) and the Socialist Republic of Romania (1947–1989).
On the other hand, Trotskyist groups have interpreted socialist democracy to be synonymous with multi-party socialist representation, autonomous union organizations, worker's control of production, internal party democracy and the mass participation of the working masses. Several parties or groups that tend to have a connection to the reunified Fourth International use this label.