The South Africa Act comes into force, establishing the Union of South Africa.

The South Africa Act 1909 was an act of the Parliament of the United Kingdom that created the Union of South Africa out of the former Cape, Natal, Orange River, and Transvaal colonies. The act also allowed for potential admission of Rhodesia into the Union, a proposal rejected by Rhodesian colonists in a 1922 referendum. The draft proposal was supported by the four colonial parliaments, but was opposed by Cape Colony premier W. P. Schreiner, who raised concerns that it would strip rights from non-white South Africans.

The Union of South Africa was the historical predecessor to the present-day Republic of South Africa. It came into existence on 31 May 1910 with the unification of the Cape, Natal, Transvaal, and Orange River colonies. It included the territories that were formerly part of the South African Republic and the Orange Free State.