An Old World primate in the gibbon family. It is found in Indonesia on the island of Sumatra, Malaysia, and southern Thailand. The species is listed as endangered on the IUCN Red List due to habitat destruction and the pet trade.

The agile gibbon has fur varying in color from black to red-brown. Its brow is white, and the male can be recognized by its white or light-grey cheeks. Additionally, the male is slightly larger than the female. The agile gibbon weighs from 4 to 6 kg (8.8 to 13 lb) with an average of 5 kg (11 lb), though in captivity it can reach 8 kg (18 lb). It has a head and body length of 44–63.5 cm (17–25.0 in). Like all gibbons it is tailless.

With its long arms they swing on branches, brachiating at a fast pace. Like all gibbons, it lives in serially monogamous pairs in a strictly enforced territory, which is defended with vigorous visual displays and songs. The diet of the agile gibbon is generally frugivorous but have also been observed each leaves, flowers, and insects.

Females give birth to a single offspring after seven months' gestation. The young gibbon is weaned at barely 2 years of age. When fully mature, at about 8 years, it leaves its family group in order to look for a mate.

The agile gibbon is found on Sumatra southeast of Lake Toba and the Singkil River, in a small area on the Malay Peninsula, and south Thailand near the Malaysian border. It predominantly lives arboreally in rain forests and rarely comes to the ground.