Major Works:
* History of South Africa, 1488-1834 (5 volumes, 1888-1903): This comprehensive work is his magnum opus, tracing the history of South Africa from the arrival of the Portuguese to the beginning of the Great Trek.
* History of the Boers in South Africa (2 volumes, 1887): Focuses on the history of the Afrikaner people in South Africa.
* Records of the Cape Colony, 1793-1806 (9 volumes, 1897-1905): A valuable collection of primary sources documenting the period of British rule in the Cape Colony.
* Ethnography and Condition of South African Tribes (1919): A significant work on the indigenous people of Southern Africa.
* The Story of the Nations: South Africa (1899): A more accessible narrative history of South Africa for a general audience.
Other Notable Works:
* The Yellow Peril in South Africa (1907): A work on the impact of Chinese immigrants in South Africa.
* The Rise and Fall of the Dutch Republics (1913): Explores the history of the Boer republics in South Africa.
* The History of the Native Races of South Africa (1910): A study of the indigenous people of South Africa.
Theal's writings are invaluable for understanding the history of South Africa and remain important resources for scholars and researchers today.