The Left-Communists were a group of those on the left-wing of Bolshevism in the aftermath of the October Revolution of 1917 in Russia. They were a orthodox-Marxist grouping led by Nikolai Bukharin and first signalled their existence in the controversies about the Brest-Litovsk peace negotiations between Russia and Germany, which they opposed on the grounds that the war should be transformed into a "revolutionary war" which would secure Proletarian Revolution across the world. They lost out in this argument and turned their attention to domestic matters.

They began to publish a newspaper, Kommunist which offered a critique of the direction in which the Communist Party of the Soviet Union was heading. They argued against the over-bureaucratisation of the state, and argued that nationalisation should be moved at a pace quicker than Lenin desired. They also felt that a classless society had failed to be secured by the revolution and that such should be effected immediately.

The Left-Communists faded as Lenin proved too strong a figure to argue against. They also lost Bukharin as a leading figure as he moderated his own position and was accommodated by Lenin.

As a group they influenced the later internal left-wing faction the Workers' Opposition as well as groups abroad such as the Spartacist League.

Lenin described left-wing communism as an "infantile disorder".