The Grotte de Fontanet is an ornate cave located on the territory of the commune of Ornolac-Ussat-les-Bains in the department of Ariège, in France.

The cave is known in the nineteenth century and the ornate gallery is discovered on February 6, 1972, by Luc Wahl. It has yielded archaeological remains dating back to the Upper Paleolithic. It is closed to visitors.

The first visits for archaeological purposes are made in the nineteenth century. The upper floor was explored by Antonin Gadal in 1930-1950 in search of Cathar traces. In 1940-1947, Denis Cathala, Gally, Mauras, and Delteil traveled the river. In 1961, the siphon was crossed by Robert Lacroux. In 1972, Luc Wahl found prehistoric drawings in an adjacent gallery. The cave reveals handprints and footprints in clay, drawings, engravings, and wall paintings, which the analyses relate to the Middle Magdalenian or Upper Magdalenian period.

The wall paintings were discovered in 1972 and the bones on the ground were studied in 1978.

An archaeoacoustic study was conducted by the musicologist Iégor Reznikoff and the prehistorian Michel Dauvois in 1988 in three Ariège caves: Grotte du Portel, Grotte de Niaux and Fontanet .