Clearwater Cave, Underground cave system in Miri, Malaysia.

Clearwater Cave (Gua Air Jernih) is a limestone cave system in Gunung Mulu National Park, Sarawak, lying mainly under the western margins of Gunung Api between the Melinau Gorge and Cave of the Winds. Its passages carry a clear stream fed by mountain springs, and the water flows out into the Melinau River. By November 2025 the surveyed length reached 265.882 km, making it the world's seventh longest cave.

Scientific teams started exploring the system during the 1970s and gradually uncovered the vast network of passages beneath the forest. The discoveries revealed this to be one of the largest cave systems connected to Gunung Mulu National Park.

Indigenous communities of Sarawak have maintained connections to these caves, incorporating them into their traditional practices and knowledge systems.

Tours are booked at the Gunung Mulu National Park headquarters, and the visit begins with a boat ride on the Melinau River to the cave entrance. Swimming in the cave's clear water is allowed only when the river discharge is low. The water comes from mountain springs and can be drunk without filtering.

The water comes from mountain springs and is clear enough to drink without filtering. When river discharge is low, swimming in the cave's river is permitted. The stream then flows out into the Melinau River, and explorers have searched for a link with Racer Cave that would join the two into one vast complex.