French Cochinchina (sometimes spelled Cochin-China) (French: Cochinchine Française, Vietnamese: Nam Kỳ, Hán tự: 南圻), was a colony of French Indochina, encompassing the Cochinchina region of southern Vietnam. Formally called Cochinchina, it was renamed in 1946 as Autonomous Republic of Cochinchina, a controversial decision which helped trigger the First Indochina War. In 1948, the autonomous republic, whose legal status had never been formalized, was renamed as the Provisional Government of South Vietnam (not to be confused with the 1969–1976 Viet Cong government). It was reunited with the rest of Vietnam in 1949.
In Vietnamese, Cochinchina was called Nam Kỳ (Southern country) although the independentists preferred to use the term Nam Bộ (Southern region).
For a series of complex reasons, the French government of Napoleon III, with the help of Spanish troops arriving from the colonial Philippines in the Spanish East Indies, invaded the southern part of Vietnam, then known in the West as Cochinchina. In September 1858, France occupied Đà Nẵng (Tourane). On February 18, 1859, they conquered Saigon and three southern Vietnamese provinces: Biên Hòa, Gia Định and Định Tường; the Vietnamese government was forced to cede those territories to France in June 1862.
In 1867, the provinces of Châu Đốc, Hà Tiên and Vĩnh Long were added to French-controlled territory. In 1864 all the French territories in southern Vietnam were declared to be the new French colony of Cochinchina, which would be governed by Admiral Marie Jules Dupré from 1871 to 1874.
In 1887, it became part of the Union of French Indochina. Unlike the protectorates of Annam protectorate and Tonkin protectorate, Cochinchina was ruled directly by the French, both de jure and de facto, and was represented by a deputy in the National assembly. Together with Tonkin, it was one of the economic centers of French Indochina.
Fifty-one Vietnamese rebels were executed following the 1916 Cochinchina uprising. In 1933, the Spratly Islands were annexed to French Cochinchina. In July 1941, Japanese troops were based in French Cochinchina (a de facto occupation). After the Japanese surrendered in August 1945, Cochinchina was returned to French rule.
In 1945, Cochinchina was ruled directly by the Japanese after they had taken over from the French in March. In August, it was briefly incorporated into the Empire of Vietnam. Later that month, the Japanese surrendered to the Việt Minh during the August Revolution. On September 2, 1945 Việt Minh established Democratic Republic of Vietnam with territory of Annam, Tonkin and Cochinchina. The independentists held the general election on January 6, 1946 in order to establish the first National Assembly in Vietnam. The elections were supposedly organized in all areas of Vietnam including Cochinchina, but the southern colony was by then back under the control of the French.
On June 1, 1946, whilst the Viet Minh leadership was in France for negotiations, southern autonomists proclaimed a government of Cochinchina, at the initiative of High Commissioner d'Argenlieu and in violation of the March 6 Ho–Sainteny agreement. The colony was proclaimed an "Autonomous Republic" . War between France and the Viet Minh followed (1946–54). Nguyễn Văn Thinh, the first head of its government, died in an apparent suicide in November of the same year. He was succeeded by Lê Văn Hoạch, a member of the caodaist sect. In 1947, Nguyễn Văn Xuân replaced Lê and renamed the "Provisional Government of the Autonomous Republic of Cochinchina" as the "Provisional Government of South Vietnam", overtly stating his aim to reunite the whole country.
The next year, the Provisional Central Government of Vietnam was proclaimed with the merger of Annam and Tonkin : Xuân became its Prime minister and left office in Cochichina, where he was replaced by Trần Văn Hữu. Xuân and the French had agreed to reunite Vietnam, but Cochinchina posed a problem because of its ill-defined legal status. The reunification was opposed by the French colonists, who were still influential in the Cochinchinese council, and by Southern Vietnamese autonomists: they delayed the process of reunification by arguing that Cochinchina was still legally a colony - as its new status as a Republic had never been ratified by the French National Assembly - and that any territorial change therefore required the approval of the French parliament. Xuân issued a by-law reuniting Cochinchina with the rest of Vietnam, but it was overruled by the Cochinchinese council.
Cochinchina remained separated from the rest of Vietnam for over a year, while former Emperor Bảo Đại - whom the French wanted to bring back to power as a political alternative to Ho Chi Minh - refused to return to Vietnam and take office as head of state until the country was fully reunited. On March 14, 1949, the French National Assembly voted a law permitting the creation of a Territorial Assembly of Cochinchina. This new Cochinchinese parliament was elected on April 10, 1949, with the Vietnamese representatives then becoming a majority. On April 23, the Territorial Assembly approved the merger of the Provisional Government of South Vietnam with the Provisional Central Government of Vietnam. The decision was in turn approved by the French National Assembly on May 20, and the merger was effective on June 4. The State of Vietnam could then be proclaimed, with Bảo Đại as head of state.