The Clearwater Cave System in Gunung Mulu National Park, Sarawak, Malaysia is believed to be one of the largest interconnected cave systems in the world by volume and the 9th longest cave in the world at 236.796 km. The system lies mainly under the western margins of Gunung Api between the Melinau Gorge and Cave of the Winds.
The first exploration by speleologists was during the 1977/78 Royal Geographical Society Mulu Sarawak Expedition when 24 km of the cave passage were surveyed. Many expeditions by the Mulu Caves Project have increased the explored length and will continue to do so for the foreseeable future.