The Tonkin Expeditionary Corps was a French military command based in northern Vietnam (Tonkin) from June 1883 to April 1886. The expeditionary corps fought the Tonkin Campaign (1883–86) taking part in campaigns against the Black Flag Army and the Chinese Yunnan and Guangxi Armies during the Sino-French War and the period of undeclared hostilities that preceded it, and in important operations against Vietnamese guerrilla bands during the subsequent 'Pacification of Tonkin'.

The Tonkin campaign was an armed conflict fought between June 1883 and April 1886 by the French against, variously, the Vietnamese, Liu Yongfu's Black Flag Army and the Chinese Guangxi and Yunnan armies to occupy Tonkin and entrench a French protectorate there. The campaign, complicated in August 1884 by the outbreak of the Sino-French War and in July 1885 by the Cần Vương nationalist uprising in Annam, which required the diversion of large numbers of French troops, was conducted by the Tonkin Expeditionary Corps, supported by the gunboats of the Tonkin Flotilla. The campaign officially ended in April 1886, when the expeditionary corps was reduced in size to a division of occupation, but Tonkin was not effectively pacified until 1896.