The fossa (Cryptoprocta ferox) is carnivorous mammal endemic to Madagascar. It is a member of the Eupleridae, a family of carnivorans closely related to the mongoose family. Its classification has been controversial because its physical traits resemble those of cats, yet other traits suggest a close relationship with viverrids (e.g. bearcat).

The fossa is the largest mammalian carnivore on the island of Madagascar and has been compared to a small cougar. Adults have a head-body length of 70–80 cm (28–31 in) and weigh between 5.5 and 8.6 kg (12 and 19 lb), with the males larger than the females. It has semi-retractable claws (meaning it can extend but not retract its claws fully) and flexible ankles that allow it to climb up and down tre ...