The Fossa (Cryptoprocta ferox) is a carnivorous mammal in the Eupleridae family of euplerids and mongooses.

The Fossa looks like a cross between a large mongoose and a small cougar. It has cat-like features, but with a longer, slimmer body than a cat. Its fur is short, straight, and reddish brown, or light and dark-brown. It has large, rounded ears, brown eyes, and a short, rounded nose with whiskers.

It has semi-retractable claws – it can extend its claws but they cannot retract fully into their big paws. It has flexible ankles that enable it to climb up and down trees head-first. It can also jump from tree to tree. It has a long tail. It has scent glands.