Indochina was the name of the French colony that eventually became Vietnam. It had three major regions, Tonkin in the north, containing the Red River delta; the central section of Annam (excluding the Central Highlands); Cochinchina in the south, containing the Mekong River. The central highlands, traditional home of the Montagnard peoples, was treated separately by the French. Laos and Cambodia were under the same French administrations, and are sometimes included in the term "French Indochina".
Indochina was originally conquered in 1858, with a formal treaty in 1862. It existed until 1954.