The François’ langur, also known as the Francois’ leaf monkey, Tonkin leaf monkey, or white side-burned black langur is a species of lutung and the type species of its species group. It is one of the least studied of the species belonging to the Colobinae subfamily.
The species is distributed from Southwestern China to northeastern Vietnam. The total number of wild individuals is unknown, but fewer than 500 are believed to be left in Vietnam and 1,400–1,650 in China. About 60 langurs are in captivity in North American zoos. The species is named after Auguste François (1857–1935), who was the French Consul at Lungchow in southern China.
Infants are born with bright orange coloured fur, which fades to black throughout the period of infancy lasting several months. It isn’t known why their coats are so conspicuous, but current hypotheses suggest it may elicit attention, protection and caregiving by adults.