The Gyr Falcon (Falco rusticolus), also spelled Gyrfalcon, is a large bird of prey. This species breeds on Arctic coasts and islands of North America, Europe and Asia. It is mainly resident, but some birds disperse more widely, after the breeding season, or in winter.

It is a bird of tundra and mountains, with cliffs or a few patches of trees. It lays 2-6 eggs on a cliff ledge nest.

This is the largest falcon, at more than 60cm in length with a wingspan up to 130cm, similar to the Common Buzzard. It is like a large Peregrine Falcon in general structure, but broader-winged and longer-tailed than that species. It usually hunts by horizontal pursuit, rather than the Peregrine's stoop from a height, and takes bird and small mammal prey such as Ptarmigans and lemmings.

Plumage is very variable in this species, although typically adults have slate-grey back and wings, and young birds are browner. Sexes are similar. Greenland Gyr Falcons have white plumage, flecked with grey on the back and wings. Other geographical forms are varying intensities of grey in coloration, with Icelandic breeders being the palest, and Eurasian birds considerably darker.