Lake Poso (Indonesian: Danau Poso) is a lake in Central Sulawesi, Indonesia, and the third-deepest lake in Indonesia. The lake contains various fish, including the eel Anguilla marmorata which migrates between the lake and the sea, and 11 fish species that are endemic to the lake, notably Adrianichthys, Mugilogobius sarasinorum, Nomorhamphus celebensis, Oryzias nebulosus, O. nigrimas, O. orthognathus and Weberogobius amadi, which are all highly threatened (in some cases possibly already extinct). There is also a large number of endemic Tylomelania freshwater snails in the lake, as well as several endemic Caridina shrimps and Parathelphusid crabs (genera Migmathelphusa, Parathelphusa and Sundathelphusa).
The town of Pendolo is situated at the southern end of the lake, the town of Tentena is located at the northern end, while a number of smaller villages dot the shoreline. The lake drains into the Poso River at Tentena, which flows into the Molucca Sea at the town of Poso. A park containing wild orchids is located near the village Bancea on the lake. As well the forests surrounding the lake still provide rare sightings of the anoa (dwarf buffalo) and the babirusa (literally, pigdeer), a ruminant pig. These two endangered species are among a number of wildlife species found only on the island of Sulawesi.