Oliver Reginald Tambo (27 October 1917 - 24 April 1993) was a South African anti-apartheid politician and a central figure in the African National Congress (ANC). He was born in Mbizana in eastern Mpondoland in what is now Eastern Cape.

In 1940 he, along with several others including Nelson Mandela, was expelled from Fort Hare University for participating in a student strike. In 1942 Tambo returned to his former high school in Johannesburg to teach science and mathematics.

Tambo, along with Mandela and Walter Sisulu, was a founding member of the ANC Youth League in 1943, becoming its first National Secretary and later a member of the National Executive in 1948. The youth league proposed a change in tactics in the anti-apartheid movement. Previously the ANC had sought to further its cause by actions such as petitions and demonstrations; however, the Youth League felt these actions were insufficient to achieve the group's goals and proposed their own 'Programme of Action'. This programme advocated tactics such as boycotts, civil disobedience, strikes and non-collaboration.

In 1955 Tambo became Secretary General of the ANC after Walter Sisulu was banned by the South African government under the Suppression of Communism Act. In 1958 he became Deputy President of the ANC and in 1959 was served with a five year banning order by the government.

In response, Tambo was sent abroad by the ANC to mobilise opposition to apartheid. He was involved in the formation of the South African United Front, which helped bring about South Africa's expulsion from the Commonwealth in 1961. In 1967, Tambo became Acting President of the ANC, following the death of Chief Albert Lutuli. In 1985 he was re-elected President of the ANC. In 1989 he suffered a debilitating stroke, but continued on as a symbol of the anti-apartheid movement both abroad and in South Africa.

He returned to South Africa in 1991 after over 30 years in exile in Zambia, and was elected National Chairperson of the ANC in July of the same year. Tambo died due to complications from a second stroke on April 24, 1993.

In 2004 he was voted 31st in the SABC3's Great South Africans.

In late 2005 ANC politicians announced plans to rename Johannesburg International Airport after him.