The Sumatran orangutan is one of the three species of orangutans. Critically endangered, and found only in the north of the Indonesian island of Sumatra, it is rarer than the Bornean orangutan but more common than the recently identified Tapanuli orangutan, also found in Sumatra. Its common name is based on two separate local words, "orang" and "hutan" ("forest"), derived from Malay, and translates as 'person of the forest'.

Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus Pongo, orangutans were originally considered to be one species. From 1996, they were divided into two species: the Bornean orangutan and the Sumatran orangutan. A third species, the Tapanuli orangutan, was identified definitively in 2017. The orangutans are the only surviving species of the subfamily Ponginae, which diverged genetically from the other hominids between 19.3 and 15.7 million years ago.