in Soviet history, one of a group within the Communist Party which in the first half of 1918 opposed Lenin's practical policies for preserving Communist rule in Russia. The group was led by Nikolay I. Bukharin.

Rather than make peace, the Left Communists favoured waging a revolutionary war. They contended that it was impossible for Soviet Russia, an economically underdeveloped country, to build Socialism until other Socialist revolutions succeeded in western Europe.

On the industrial issue, the Left Communists insisted that the proletariat should run the economy and that the workers' control of industrial enterprises that had developed during 1917 was a step toward this goal and should not be sacrificed for short-range, opportunistic purposes.

The Left Communists initially had substantial support within the party. They dominated the Supreme Council of National Economy, an institution created in December 1917 to supervise the economy; in January 1918 there were more votes in the Central Committee favouring a revolutionary war than a peace treaty. But in March 1918 they were defeated at the seventh Party Congress, which approved the Brest-Litovsk peace treaty; they also lost their positions on the Supreme Council of National Economy and shortly afterward lost their control of the Moscow and Urals regional organizations. When the Soviet government nationalized all large industrial enterprises in late June, many Left Communists considered this to be a correct economic policy and shifted their support back to Lenin. By the end of the summer the Left Communists no longer existed as a distinct opposition group.