The narwhal (Monodon monoceros), is a species of toothed whale. It is the only species in the genus Monodon. The most prominent feature of the species is an adult male's long single tusk that can be up to 3 m (9.8 ft). The narwhal has a mottled pigmentation, with blackish-brown markings over a white background. An adult narwhal is typically 3.0 to 5.5 m (9.8 to 18.0 ft) in length and 800 to 1,600 kg (1,800 to 3,500 lb) in weight. Instead of a dorsal fin, it possesses a shallow dorsal ridge. Carl Linnaeus scientifically described the species in 1758 in his work Systema Naturae.

The narwhal inhabits Arctic waters, and is vulnerable to predatory attacks from polar bears, orcas and humans. Narwhals typically visit Baffin Bay between June and September. After this period, they move to the Davis Strait, a journey that spans around 1,700 km (1,100 mi), and stay there until April. Its prey mostly consists of Arctogadus glacialis, Boreogadus saida, Greenland halibut, cuttlefish, shrimp, and armhook squid. The narwhal is one of the deepest-diving marine mammals, with many individuals diving at depths of over 1,500 m (5,000 ft). It mates in the offshore pack ice in April or May, and has a gestation lasting an average of 15 months. Like most other cetaceans, the narwhal uses clicks, whistles and knocks to communicate with others of its kind.

There are estimated to be 170,000 living narwhals, and the species is listed as least concern by the International Union for Conservation of Nature. The narwhal has been hunted for hundreds of years by Inuit in northern Canada and Greenland for meat and ivory and a regulated subsistence hunt continues.