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The following lists events that happened during 1921 in South Africa.
Incumbents
- Monarch: King George V
- Governor-General and High Commissioner for Southern Africa: Prince Arthur of Connaught
- Prime Minister: Jan Smuts
- Chief Justice: James Rose Innes
Events
;May
- 3 – The second census of the Union of South Africa takes place.
- 24 – The Bulhoek Massacre takes place with an estimated 163 killed.
;July
- 30 – The Communist Party of South Africa is established.
;December
- 28 – White gold miners on the Witwatersrand go on strike in the Rand Rebellion.
;Unknown date
- Dagbreek men's residence opens at Stellenbosch University.
Births
- 30 May – Jamie Uys, actor and film director. (d. 1996)
- 21 July – Vusamazulu Credo Mutwa, Zulu sangoma and author (d. 2020)
Deaths
- 10 September – John Tengo Jabavu, editor of South Africa's first newspaper in Xhosa. (b. 1859)
Railways
Railway lines opened
thumb|[[South African Class GA 2-6-0+0-6-2|Class GA]]
thumb|[[South African Class GB 2-6-2+2-6-2|Class GB]]
- 1 November – Transvaal – Pretoria West to Roberts Heights, .
- 28 November – Natal – Booth Junction to Cato Ridge, .
- June – The first of seven Class GB 2-6-2+2-6-2 Garratt locomotives.
