The Communist Party of Britain (CPB) is a communist party in Great Britain which emerged from a dispute between Eurocommunists and Marxist-Leninists in the Communist Party of Great Britain in 1988. It follows Marxist–Leninist theory and supports what it regards as existing socialist states. The party has fraternal relationships with the ruling parties in Cuba, China, Laos, and Vietnam. It is affiliated nationally to the Cuba Solidarity Campaign and the Venezuela Solidarity Campaign. It is a member of the International Meeting of Communist and Workers' Parties, together with 117 other political parties. After the fall of the Soviet Union, the party was one of two original British signatories to the Pyongyang Declaration.

The Communist Party of Britain was established in April 1988 by a disaffected section of the Communist Party of Great Britain (CPGB). This section sought to preserve the Communist Party, saving it from its forthcoming dissolution under a revisionist, Eurocommunist leadership.

In the period leading up to 1988, the Communist Party of Great Britain was in turmoil as the leadership fought the Marxist–Leninist tendencies inside the party. The rupture was made publicly visible in August/September 1982 after the CPGB's theoretical journal Marxism Today published a feature article by Tony Lane which was critical of the labour movement. The CPGB-affiliated Morning Star newspaper responded with a front-page article by the party's Industrial Organiser Mick Costello criticising the Marxism Today article. The CPGB's executive committee was flooded with communication from party branches over the affair. The party did not withdraw support for Marxism Today, but the editorial board did introduce a disclaimer that 'the views expressed by authors are personal and not necessarily those of the editor or editorial board', marking the journal's deviation from the party line.

Both publications came to characterise separate visions for the future of the party; the internal opposition rallied around the Morning Star and the reformist leadership around Marxism Today. These early signs of trouble attracted international attention, notably from the East German SED which was concerned about the Eurocommunist tendency in the CPGB.

At the CPGB's 38th congress in November 1983, Tony Chater the editor of the Morning Star, as well as the assistant editor David Whitfield, were both removed from their positions on the party's executive. However, they were able to keep their positions at the paper, as it is owned and managed separately by the People's Press Printing Society co-operative. The following year at the PPPS Annual General Meeting in June 1984, a majority of delegates re-elected Chater and Whitfield to the management committee of the newspaper, against the wishes of the CPGB leadership. In November 1984, the North-West District Congress elected an opposition majority to its District Committee, to which the leadership responded by declaring the district election illegitimate. A similar movement was brewing in London, where the CPGB General Secretary Gordon McLennan pre-emptively dissolved the London District Congress and 11 members of the District Committee were suspended. In Scotland, 20 branches were brought under disciplinary sanctions. The CPGB Executive Committee then brought the dispute to a special congress on 18–20 May 1985, with a draft resolution condemning the Morning Star and the group around it. Over 650 amendments were submitted to the resolution, which was eventually passed after a long debate, and followed up by the expulsion of eighteen members.

In June 1985, dissident and expelled members of the CPGB formed the Communist Campaign Group. This group declared itself loyal to the party programme, and stated its aim was to prevent the liquidation of the party. The Campaign Group was provided an office within the premises of the Morning Star. The first post-congress meeting of the new CPGB Executive Committee in July 1985 dropped the commitment for party members to support the Morning Star; it concluded with the dissolution of more branches and further disciplinary measures, such as the expulsion of Ken Gill.

For two years, the Campaign Group organised within the CPGB to defend the party's Marxist–Leninist principles. However, at the 1987 party congress the Campaign Group failed to shift the leadership, and the direction of the CPGB diverted towards transformation into a social-democratic party. Kevin Halpin was invited to Moscow to discuss the possibility that the CPGB would break apart, he was advised by the CPSU that the Campaign Group should continue working within the existing party structures. On 8 January 1988 the Campaign Group called a press conference to announce the formation of the Communist Party. The re-establishment congress took place over the weekend of 23–24 April 1988, where one of the prominent leaders of the Campaign Group, Mike Hicks, was elected to the position of General Secretary. Chater emphasised the continuity with the CPGB at the congress, explaining at the time:

We are not creating a new Party. We are re-establishing the Party on the basis of its' [sic] rules and programme.