Lake Kutubu is a lake in the Southern Highlands Province of Papua New Guinea. It lies to the east of the Kikori River, into which it eventually drains. It is about 50 km southwest of Mendi, the provincial capital. It is one of the few lakes in the country that occurs in a depression in the rugged interior mountains. It is the second-largest lake in Papua New Guinea, after Lake Murray, and, at 800 m above sea level, the largest upland lake. The area of the lake is 49.24 km², while the total catchment area is 250 km². Lake Kutubu and Lake Sentani form an ecoregion on the WWF's Global 200.