The Bornean Flat-headed Frog (Barbourula kalimantanensis) is a species of toad in the Bombinatoridae family. It is the second frog known to have no lungs.
The frog, no more than 70 mm (2.8 in) long, lives in cold, clear, and fast rivers in remote areas of the rainforests of Kalimantan, the Indonesian part of the island of Borneo. Its natural habitats are rivers in tropical moist lowland forests. It is threatened by habitat loss from severe degradation of the river habitats by increased turbity and toxic metals used in mining and other unfortunate consequences of development on the island.