The Greenville Saltpeter Cave is in Greenville, Monroe County. This is a noncommercial "wild" cave and is not open to the general public. The cave has four entrances and 3.8 miles of surveyed passages. The southern entrance is above the mill pond and is the place where Laurel Creek, which sinks about one mile north of Greenville, reemerges from the ground. The three northern entrances to the cave are in a small valley about a third of a mile north of the mill pond entrance. One of these, the northeastern entrance, is called the water entrance and is situated where a portion of the underground route of Laurel Creek is exposed to the surface.

The cave was owned by John Maddy in 1804 and then sold to Jacob and John Mann who manufactured saltpeter (potassium nitrate) at the site for several years. Saltpeter was used in the manufacture of gunpowder. The cave was again mined for saltpeter during the Civil War. Unfortunately, the saltpeter section of the cave has been heavily vandalized, and few traces of mining or the old leaching hoppers remain. The cave has several large rooms but few calcite formations. The passages intertwine and form a maze. All of the entrances are on private property.

The Greenville Saltpeter Cave occurs in the Union Limestone of the Greenbrier Group (Mississippian age). The cave was designated a National Natural Landmark in 1973. In 2023, it was acquired by the West Virginia Land Trust to be managed as the Greenville Saltpeter Cave Preserve, in cooperation with the Division of Natural Resources, U.S. Fish and Wildlife, and the Institute for Earth Education.

The cave is home to several endangered species, including the Indiana bat, northern long-eared bat, tricolored bat, and little brown bat. The tricolored bats in the cave constitute one of the largest surviving groups anywhere.