Halibut is a flatfish and a right-eyed flounder. The name is derived from haly (holy) and butt (flat fish), for its popularity on Catholic holy days. Halibut is a highly regarded fish for consumption. The Atlantic halibut is among the largest of bony fishes in the world with a maximum recorded size of more than 15 feet.

Halibut is found over most of the North Atlantic and a close relative, the Pacific halibut (Hippoglossus stenolepis) is to be found in the North Pacific. Its habitat is all around Iceland but is more common in the warmer waters to the south and west of the country. It is flattened sideways and habitually lies on the left side of its body with both eyes migrating to the right side of its head during development. Its upper surface is a uniformly dark chocolate, olive or slate color, and can be almost black; the underside is pale. The end of the caudal fin is concave. Young fish are paler with more mottled coloration.