The Communist League was a small organisation of the far left in the United Kingdom. It was founded in March 1919 by the London District Council of the Socialist Labour Party and various anarchist groups in London and Scotland. These included Guy Aldred's Glasgow Anarchist Group. In contrast to the nascent Communist Party of Great Britain, it opposed participation in Parliamentary elections and emphasised the formation of Soviets over work in the trade unions.
The group began publishing a paper, The Communist, and entered into negotiations with the aim of merging with the Workers' Socialist Federation. It also gained the support of some miners in Treherbert. Attempts to open discussions with the Independent Labour Party, the Socialist Labour Party (SLP) and the British Socialist Party did not prove fruitful.
The Communist League decided to imitate Sinn Féin's abstentionist tactic of using elections as a platform for their propaganda, while pledging not to take their seats if elected. Their proposal was not put into action, and the SLP did not accept their offer to support an SLP candidate who stood on this platform.
Tensions between the anarchists and the Marxists in the group led to its dissolution in early 1920. Aldred went on to found the Anti-Parliamentary Communist Federation the following year.