Prior to 2017, there were two species of orangutan: the Bornean (Pongo pygmaeus) and the Sumatran (Pongo abelii). A third species, the Tapanuli orangutan (Pongo tapanuliensis) was described in 2017. (Tapanuli is a small area of Sumatra.)
There may have been a fourth species, now extinct: the Vietnamese orangutan (Pongo hooijeri). To quote Wikipedia: "It is unclear whether [this] is truly a distinct species or merely a Vietnamese population of one of the extant orangutan species."
Orangutan can, if you prefer, be written as orang–utan, orang utan, orangutang, or ourang–outang.
© Haydn Thompson 2017–21