一角鲸（学名：Monodon monoceros；英文名：Narwhal）又称独角鲸和长枪鲸，在一般人的印象中总是与传说中的独角兽（Unicorn）联想在一起，理由很明显：雄性一角鲸长有长而呈螺旋状的长牙，让牠们比世界上任何生物都要接近传说中独角兽的形象。事实上在中世纪以前，商人与炼金术士将一角鲸视为神秘的生物，其长牙被当作「独角兽的角」，价值非凡。虽然现今已不再将牠们与独角兽作联想，但由于一角鲸所处的遥远而严峻寒冷的北极，与其独特的外观，牠们仍然是令人着迷的生物。

The narwhal, or narwhale (Monodon monoceros), is a medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth. It lives year-round in the Arctic waters around Greenland, Canada, and Russia. It is one of two living species of whale in the Monodontidae family, along with the beluga whale. The narwhal males are distinguished by a long, straight, helical tusk, which is an elongated upper left canine. The narwhal was one of many species described by Carl Linnaeus in his publication Systema Naturae in 1758.