}

The Union of South Africa is the historic predecessor to the present-day state of the Republic of South Africa. It came into being on 31 May 1910, with the previously separate colonies of the Cape, Natal, Transvaal and the Orange Free State becoming Provinces in the Union of South Africa.

It was founded as a dominion, later Commonwealth realm, but became a republic on 31 May 1961, henceforth known as the Republic of South Africa.