The Siamang (Symphalangus synactylus) is a tailless, arboreal, black furred gibbon native to the forests of Malaysia, Thailand, and Sumatra. The largest of the lesser apes, the Siamang can be twice the size of other gibbons, reaching 1 m in height, and weighing up to 23 kg. The Siamang is the only species in the genus Symphalangus.