The Gyrfalcon is the largest falcon in the world. Despite its size, it maintains a falcon-like profile with a long tail and long wings.
Its wings are broader and more blunt at the tips than many other falcons. The plumage of the Gyrfalcon can take three main forms, white, gray, and dark, with many intermediate plumages.
White adults have almost pure white breasts and bellies. The rest of their bodies are white mottled with brown.
They have dark wingtips. Gray adults have gray upperparts with subtle darker mottling, and white underparts mottled with gray. Dark adults are dark-brownish overall above and brown streaked with white below.
There is extreme sexual size dimorphism among Gyrfalcons, with males being only about 65% the size of females.