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.

The Black Flag Army was a splinter remnant of a bandit group recruited largely from soldiers of ethnic Zhuang background, who crossed the border in 1865 from Guangxi, China into northern Vietnam, during the Nguyễn dynasty. Although brigands, they were known mainly for their fights against the invading French forces, who were then moving into Tonkin. The Black Flag Army is so named because of the preference of its commander, Liu Yongfu, for using black command flags.