The beluga whale (Delphinapterus leucas) is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus. It is also known as the white whale, as it is the only marine mammal of this colour; the sea canary, due to its high-pitched calls; and the melonhead, though that more commonly refers to the melon-headed whale, which is an oceanic dolphin.

The beluga is adapted to life in the Arctic, so has anatomical and physiological characteristics that differentiate it from other cetaceans. Amongst these are its all-white colour and the absence of a dorsal fin, which allows them to swim under ice with ease. It possesses a distinctive protuberance at the front of its head which houses an echolocation organ called the melon, which in this species is large and deformable. The beluga's body size is between that of a dolphin's and a true whale's, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,530 lb). This whale has a stocky body. A large percentage of its weight is blubber (subcutaneous fat), as is true of many cetaceans. Its sense of hearing is highly developed and its echolocation allows it to move about and find breathing holes under sheet ice.

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