French Indochina, officially known as the Indochinese Union and after 1947 as the Indochinese Federation, was a grouping of French colonial territories in Mainland Southeast Asia until its end in 1954. It comprised Cambodia, Laos, the Chinese territory of Guangzhouwan, and the Vietnamese regions of Tonkin in the north, Annam in the centre, and Cochinchina in the south. The capital for most of its history (1902–1945) was Hanoi; Saigon was the capital from 1887 to 1902 and again from 1945 to 1954.

The French colonial empire comprised the overseas colonies, protectorates, and mandate territories that came under French rule from the 16th century onward. A distinction is generally made between the "First French colonial empire", that existed until 1814, by which time most of it had been lost or sold, and the "Second French colonial empire", which began with the conquest of Algiers in 1830. On the eve of World War I, France's colonial empire was the second largest in the world after the British Empire.