The Tapanuli orangutan is a species of orangutan restricted to South Tapanuli in the island of Sumatra in Indonesia. It is one of three known species of orangutan, alongside the Sumatran orangutan, found farther northwest on the island, and the Bornean orangutan. It was described as a distinct species in 2017. As of 2018, there are roughly 800 individuals of this species and it is currently on the critically endangered species list.

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.