Sir Thomas Watt (1857 – 1947) was a South African politician and cabinet minister.

Watt studied at the University of Glasgow and became a lawyer. In 1883 he emigrated to Natal and settled in Dundee. After serving for Britain in the Anglo-Boer War, he was elected to the Natal Legislative Assembly and became Minister of Justice and Education for the colony and later from 1908 to 1909 a member of the National Convention which drafted the South African Act in terms of which Union was possible the following year. After the unification he became Minister of Posts and Public Works in Louis Botha's cabinet. He served under Botha and Jan Smuts fell to the South African Party in 1924 as Minister of Public Welfare, Home Affairs and Railways. He died in 1947 at the age of 90.

In 1907, the King approved the retention of the title "Honourable" as he had served for more than three years as a member of the Executive Council of the Colony of Natal.^[1] He was appointed a Knight Commander of the Order of St Michael and St George (KCMG) in the 1912 New Year Honours, having been appointed a Commander of the same Order in the 1906 Birthday Honours.^[2]