John Rex (5 March 1925 – 18 December 2011) was a South African-born British sociologist.
Born in Port Elizabeth, he was radicalised after working for the South African Bantu Affairs Administration and moved to Britain.
He was a lecturer at the universities of Leeds (1949–62) (where he was a leading left-wing activist), Birmingham (1962–64), Durham (1964–70), Warwick (1970–79 and 1984–90), Aston (1979–84), Toronto (1974–75), Cape Town (1991) and New York (1996).
He was also a member of the UNESCO International Experts' Committee on Racism and Race Prejudice (1967) and president of the International Sociological Association's Research Committee on Racial and Ethnic Minorities (1974–82).