The fossa (Cryptoprocta ferox; /ˈfɒsə/ FOSS-ə or /ˈfuːsə/ FOO-sə; Malagasy: [ˈfusə̥]) is a slender, long-tailed, cat-like mammal that is endemic to Madagascar. It is a member of the carnivoran family Eupleridae.
The fossa is the largest mammalian carnivore on Madagascar and has been compared to a small cougar, as it has convergently evolved many cat-like features. 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 trees head-first, and also support jumping from tree to tree. A larger relative of the species, Cryptoprocta spelea, probably became extinct before 1400.