'Orang' and 'utan' are the Malay words meaning 'person' and 'forest'; the orangutan is literally a 'person of the forest'. Apart from humans, the orangutan is the only one of the five great apes - the orangutan, the gorilla, the common chimpanzee, the bonobo (pygmy chimpanzee) and human - to live outside Africa and is the largest tree living mammal in the world. It is less closely related to humans than the other three great apes, but is still strangely human-looking.
The two sub-species living in Borneo and Sumatra differ a little in appearance. Sumatran orangutans are generally slimmer and lighter-coloured than their Bornean counterparts. The Bornean male has larger cheek pads than the Sumatran.
In 2017, a third species, the Tapanuli orangutan, was identified.