The Puerto Princesa Subterranean River National Park is located about 50 kilometers north of the city of Puerto Princesa, Palawan, Philippines. The National Park is located in the Saint Paul Mountain Range on the northern coast of the island.

It features a limestone karst mountain landscape with an 8.2 km. navigable underground river. A distinguishing feature of the river is that it winds through a cave before flowing directly into the South China Sea. It includes major formations of stalactites and stalagmites, and several large chambers. The lower portion of the river is subject to tidal influences. The underground river is reputed to be the world's longest and is a unesco protected "world heritage site".