Cryptoprocta spelea, also known as the giant fossa, is an extinct species of carnivore from Madagascar in the family Eupleridae which is most closely related to the mongooses and includes all Malagasy carnivorans. It was first described in 1902, and in 1935 was recognized as a separate species from its closest relative, the living fossa (Cryptoprocta ferox). C. spelea was larger than the fossa, but otherwise similar. The two have not always been accepted as distinct species. When and how C. spelea became extinct is unknown; there is some anecdotal evidence, including reports of very large fossas, that there is more than one surviving species.
The species is known from subfossil bones found in a variety of caves in northern, western, southern, and central Madagascar. In some sites, it occurs with remains of C. ferox, but there is no evidence that the two lived in the same places at the same time. Living species of comparably sized, related carnivores in other regions manage to coexist, suggesting that the same may have happened with both C. spelea and C. ferox. C. spelea would have been able to prey on larger animals than its smaller relative could have, including the recently extinct giant lemurs.
In 1902, Guillaume Grandidier described subfossil carnivoran remains from two caves on Madagascar as a larger "variety" of the living fossa (Cryptoprocta ferox), C. ferox var. spelea. G. Petit, writing in 1935, considered spelea to represent a distinct species. Charles Lamberton reviewed subfossil and living Cryptoprocta in 1939 and agreed with Petit in recognizing 2 species, naming this species from a specimen found at Ankazoabo Cave near the place Itampolo. The generic name translates to "hidden anus" referring to the fact that the anus is hidden by anal sacs in C. ferox. The specific name spelea means "cave" and was given because of the location of its discovery. However, Lamberton apparently had at most three skeletons of the living fossa, not nearly enough to capture the range of variation in that species, and some later authors did not separate C.