The South African Communist Party (SACP) is a communist party in South Africa. It was founded on 12 February 1921 as the Communist Party of South Africa (CPSA), and tactically dissolved itself in 1950 in the face of being declared illegal by the governing National Party under the Suppression of Communism Act, 1950. The Communist Party was reconstituted underground and re-launched as the SACP in 1953, participating in the struggle to end the apartheid system. It is a member of the ruling Tripartite Alliance alongside the African National Congress and the Congress of South African Trade Unions (COSATU) and through this it influences the South African government. The party's Central Committee is the party's highest decision-making structure. Although the party has not left the Tripartite Alliance, the SACP has announced its intention to break with the ANC and run its own candidates in the 2026 local elections, following the ANC's decision to enter a unity government with right-wing parties.

The Communist Party of South Africa was founded in 1921 by the joining together of the International Socialist League and others under the leadership of William H. Andrews. It first came to prominence during the Rand Rebellion, a strike by white miners in 1922. The large mining concerns, facing labour shortages and wage pressures, had announced their intention of engaging blacks in semi-skilled and some higher-level jobs at low wage rates, compared to their white counterparts who enjoyed the monopoly of higher and well-paying occupations. The CPSA supported the strike as the struggle between the working class and the capitalist class, but it distanced itself from racist slogans associated with the strike. The party said in the statement a white South Africa was impossible, and all the workers had to organise and unite regardless of their race to fight for a non-racial South Africa and better conditions for all workers.

The party thus reoriented itself at its 1924 Party Congress towards organising black workers and "Africanising" the party. By 1928, 1,600 of the party's 1,750 members were black. In the same year, the Communist International adopted a resolution for the CPSA to adopt the "Native Republic" thesis, which stipulated that South Africa is a country belonging to the natives, that is, the Indigenous Black population, and that most of South Africa's revolutionary potential laid with them. The resolution was influenced by a delegation from South Africa. James la Guma, the party Chairperson from Cape Town, had met with the leadership of the Communist International.

Contemporary scholars have argued that the party dismissed competing attempts at multiracial revolutionary organisations during this period, especially multiracial union organising by the syndicalists, and used revisionist history to claim that the party and its Native Republic policy was the only viable route to African liberation. Despite this, in 1929 the party adopted a "strategic line" which held that, "The most direct line of advance to socialism runs through the mass struggle for majority rule". By 1948, the Communist Party had officially abandoned the Native Republic policy.

In 1946, the CPSA along with the African National Congress participated in the general strike that was started by the African Mine Workers' Strike in 1946. Many party members, such as Bram Fischer, were arrested.

Aware that the National Party, elected to government in 1948, was about to ban the Communist Party, the CPSA decided by a majority to dissolve itself. A minority felt that the party should organise underground, but the majority apparently argued that this would be unnecessary, believing that support should be given to the African National Congress (ANC) in the drive to majority rule. After its voluntary dissolution, the CPSA was declared illegal in 1950. In 1953, a group of former CPSA members launched the South African Communist Party that remained — as had been the CPSA — aligned with the Soviet Union. The ban on the party was lifted in 1990 when the ANC and other anti-apartheid organisations and individuals were also unbanned, and African National Congress leader Nelson Mandela was released from prison.

The CPSA/SACP was a particular target of the governing National Party. The Suppression of Communism Act was used against all those dedicated to ending apartheid, but was obviously particularly targeted at the communists.^{[citation needed]}

Following the dissolution and subsequent banning of the CPSA, former party members and, after 1953, members of the SACP adopted a policy of primarily working within the ANC in order to reorient that organisation's programme from a nationalist policy akin to the CPSA's former Native Republic policy towards a non-racial programme which declared that all ethnic groups residing in South Africa had equal rights to the country. While black members of the SACP were encouraged to join the ANC and seek leadership positions within that organisation, many of its white leading members formed the Congress of Democrats which in turn allied itself with the African National Congress and other "non-racial" congresses in the Congress Alliance on the basis of multi-racialism. The Congress Alliance committed itself to a democratic, non-racial South Africa where the "people shall govern" through the Freedom Charter. The Freedom Charter was adopted by the ANC, the SACP and other partners in the Alliance in accordance with its evolution. The Charter has since remained the cornerstone of the Alliance, as its basic, shared programme to advance a national democratic revolution, both a process of struggle and transformation to achieve a non-racial, non-sexist, democratic and prosperous South Africa.^{[citation needed]}