The Great Black-backed Gull, Larus marinus, is a very large gull which breeds on the European and North American coasts and islands of the North Atlantic. It is fairly sedentary, but some Great Black-backed Gulls move further south or inland to large lakes or reservoirs.

This is the largest gull, much bigger than a Herring Gull and is often described as the King of Gulls.[citation needed] It is 61-74 cm long with a 1.4-1.7 m wingspan, the large adult males often weighing in at more than two kilogrammes. It is bulky, and has a powerful bill. The adults have black wings and back, with conspicuous white "mirrors" at the wing tips. The legs are pinkish, and the bill yellow with a red spot.

Young birds have scaly black-brown upperparts, and a neat wing pattern. They take at least four years to reach maturity, development in this species being somewhat slower than that of other large gulls. The call is a deep "laughing" cry.

Unlike most Larus gulls, Great Black-backed Gulls are mostly carnivorous and frequently hunt and kill any prey smaller than themselves, behaving more like a raptor than a typical larid gull, though they will also scavenge. They frequently rob other seabirds of their catch. They can swallow a puffin or a small wild duck whole.

This species breeds singly or in small colonies, making a lined nest on the ground often on top of a rocky stack. 3-5 eggs are laid.