The cougar (Puma concolor), also commonly known as the puma, mountain lion, panther or catamount, is a large felid of the subfamily Felinae native to the Americas. Its range, from the Canadian Yukon to the southern Andes of South America, is the widest of any large wild terrestrial mammal in the Western Hemisphere. An adaptable, generalist species, the cougar is found in most American habitat types. It is the biggest cat in North America, and the second-heaviest cat in the New World after the jaguar. Secretive and largely solitary by nature, the cougar is properly considered both nocturnal and crepuscular, although daytime sightings do occur. The cougar is more closely related to smaller felines, including the domestic cat (subfamily Felinae), than to any species of subfamily Pantherinae, of which only the jaguar is native to the Americas.

The cougar is an ambush predator that pursues a wide variety of prey. Primary food sources are ungulates, particularly deer. It also hunts species as small as insects and rodents. This cat prefers habitats with dense underbrush and rocky areas for stalking, but can also live in open areas. The cougar is territorial and survives at low population densities. Individual territory sizes depend on terrain, vegetation, and abundance of prey. While large, it is not always the apex predator in its range, yielding to the jaguar, gray wolf, American black bear, and grizzly bear. It is reclusive and mostly avoids people. Fatal attacks on humans are rare, but have recently been increasing in North America as more people enter cougar territories.

Intensive hunting following European colonization of the Americas and the ongoing human development of cougar habitat has caused populations to drop in most parts of its historical range. In particular, the North American cougar was extirpated in eastern North America in the beginning of the 20th century, except for the isolated Florida panther subpopulation. Transient males have been verified in Minnesota, Missouri Iowa, Michigan, Indiana, and Illinois (where a cougar was shot in the city limits of Chicago), and in at least one instance, observed as far east as coastal Connecticut. Reports of eastern cougars (P. c. cougar) still surface, although it was declared extirpated in 2011.