France colonized Vietnam, Cambodia, and Laos.
Though France had already control over the three southern provinces of Vietnam, Cochinchina, it wasn't until they won the Sino-French War (1883-1885) that they colonized Vietnam (which were divided into Annam, Tonkin and Cochinchina).
French then created a federation called French Indochina in 1887, that comprised Vietnam and Cambodia. Previously, Cambodia’s royal family had agreed to become a French protectorate to escape domination by rival regional kingdoms, in 1863.
Laos was later added after the Franco-Siamese War in 1893, in which France had won too.