A soviet (Russian: сове́т) originally was a workers' local council in late Imperial Russia. The councils and the term later were adopted by the Bolsheviks who saw it as the basic organizing unit of society.

Originally the soviets were a grassroots effort to practice direct democracy. Russian Marxists made them a medium for organizing against the state, and between the February and October Revolutions, Bolsheviks used the slogan Вся власть советам ("All power to the soviets" or "All power to the workers' councils") in opposing the Provisional Government led by Kerensky.

Following the October Revolution, all factories eventually had soviets organized according to the Bolshevik understanding of Marxist-Leninist theory, supplanting the earlier meaning that allowed for independent soviets. (Dissident existing soviets were won over or suppressed; Bolshevik soviets were organized in factories that lacked soviets.) The view was widely promoted and expressed that Bolshevik power rested on the collective will of these soviets, representing the fulfillment of the slogan.

The term also came to be used outside the Soviet Union by some Marxist-Leninist movements, for example, the Chinese Communist Party's efforts in the "Chinese Soviet Republic" immediately prior to the Long March.

Based on and in support of view of the state implicit in the Bolshevik use of the term, the word "soviet" naturally extended, or consciously was extended, to mean in effect any body formed by a group of soviets to delegate, up a hierarchy of soviets, the authority to express and effect their will. In this sense, post-Kerensky government bodies at local and republic levels (but in the Russian federated republic, local, republic, and federated republic levels) were called "soviets", and at the top of the hierarchy, the Supreme Soviet was the nominal core of the Union government of the Union of Soviet Socialist Republics, officially formed in December 1922.