The Official Languages of the Union Act, 1925 (Dutch: Wet op de Officiële Talen van de Unie, 1925 ), was an Act of the Parliament of South Africa that included Afrikaans as a variety of the Dutch language.

The Act commenced on 27 May 1925, but deemed to have had effect since the creation of the Union in 1910, having the effect of making Afrikaans an official language of the Union of South Africa since that date.

Part 8, section 137, of the South Africa Act read: Both the English and Dutch languages shall be official languages of the Union, and shall be treated on a footing of equality, and possess and enjoy equal freedom, rights, and privileges; all records, journals, and proceedings of Parliament shall be kept in both languages, and all Bills, Acts, and notices of general public importance or interest issued by the Government of the Union shall be in both languages.Doubts soon arose about the status of the Afrikaans language and whether its status as a Dutch daughter language implied it to be on equal footing.

The single substantive provision of the Official Languages Act reads: The word "Dutch" in section one hundred and thirty-seven of the South Africa Act, 1909, and wheresoever else that word occurs in the said Act, is hereby declared to include Afrikaans.The South Africa Act and the Official Languages Act were repealed by the Constitution of 1961, which reversed the position of Afrikaans and Dutch.

The Constitution of 1983 removed any mention of Dutch altogether.