English: Great Auk (Pinguinis impennis) specimen (Bird no. 8, the Glasgow Auk) and replica egg, Kelvingrove, Glasgow. A lost part of the biogeography of Britain, and the only flightless bird that has bred in Europe in historical times. The last Great Auk in Britain was killed on Stac-an-Armin, St Kilda, in about 1840 and the last pair seen alive in the world was caught and throttled on the island of Eldey, Iceland, in 1844.

Proven breeding sites for the Great Auk are few: in Britain, St Kilda was the only certain site and much of our knowledge of the species in life comes from the description given by Martin Martin following his visit there in 1697. Papa Westray in Orkney was another known haunt, with William Bullock gaining some infamy in the early 19th century for his attempts to capture the pair there, although there is no actual proof that they bred there. Bones are, however, common around early human habitations in Scotland and while these could have been brought from elsewhere, many paleozoologists suspect that there were several large colonies in Scotland which were largely wiped out by early Neolithic hunter-gatherers.

As suggested by the scientific name, the Great Auk is also probably the original 'penguin', the name assumed to be from the Welsh for white head, referring to the white flash on the forehead. Early visitors to the Antarctic presumably transferred the name to the superficially similar but unrelated birds they found there.

Nowadays, according to Errol Fuller in his book on Extinct Birds, there are just 78 Great Auk skins and about 75 eggs left in existence.