The Bar-tailed Godwit, Limosa lapponica, is a large wader in the family Scolopacidae, which breeds on Arctic coasts and tundra mainly in the Old World, and winters on coasts in temperate and tropical regions of the Old World. It makes the longest non-stop flight known for any bird and also the longest journey without pausing to feed by any animal, 11,570 km along a route from Alaska to New Zealand.

The Bar-tailed Godwit is a relatively short-legged species of godwit. The bill-to-tail length is 37–41 cm, with a wingspan of 70–80 cm. Males average smaller than females but with much overlap; males weigh 190–400 g, while females weigh 260–630 g; there is also some regional variation in size (see subspecies, below). The adult has blue-grey legs and a very long dark bill with a slight upward curve and pink at the tip. The neck, breast and belly are unbroken brick red in breeding plumage, off white in winter. The back is mottled grey.

It is distinguished from the Black-tailed Godwit by its barred, rather than wholly black, tail and a lack of white wing bars. The most similar species is the Asiatic Dowitcher.

There are three subspecies, listed from west to east:

Limosa lapponica lapponica (Linnaeus, 1758). Breeds from northern Scandinavia east to the Taymyr Peninsula; winters western coasts of Europe and Africa from the British Isles and the Netherlands south to South Africa, and also around the Persian Gulf. Smallest subspecies, males up to 360 g, females to 450 g.

Limosa lapponica menzbieri Portenko, 1936. Breeds northeastern Asia from the Taymyr Peninsula east to the Kolyma River delta; winters southeastern Asia and Australia. Intermediate between the other two subspecies.

Limosa lapponica baueri Naumann, 1836. Breeds far northeastern Asia east of the Kolyma River, and western Alaska; winters in Australia and New Zealand. Largest subspecies.

It forages by probing on mudflats or in marshes. In short vegetation, it may pick up insects by sight. It mainly eats insects and crustaceans, but also parts of aquatic plants.

The breeding habitat is Arctic Europe, Asia and western Alaska on open tundra. It nests on the ground, usually in short vegetation.

The Bar-tailed Godwit migrates in flocks to coastal western Europe, Africa, South Asia, Australia and New Zealand - where the sub-species Limosa lapponica baueri is called Kuaka in Maori.

It has recently (2007) been shown to undertake the longest non-stop flight of any bird. Using satellite tracking, birds in New Zealand were tagged and tracked all the way to the Yellow Sea in China. According to Dr. Clive Minton (Australasian Wader Studies Group) "The distance between these two locations is 9,575 km, but the actual track flown by the bird was 11,026 km. This is the longest known non-stop flight of any bird. The flight took approximately nine days. At least three other Bar-tailed Godwits also appear to have reached the Yellow Sea after non-stop flights from New Zealand."

One specific female of the flock, nicknamed "E7", flew onward from China to Alaska, and on August 29 she departed on a non-stop flight back to New Zealand, setting a new known flight record of 11,570 km.

Stray birds from Europe and Asia occasionally appear on both North American coasts.