The Adélie penguin (Pygoscelis adeliae) is a species of penguin common along the entire coast of the Antarctic continent, which is the only place where it is found. It is the most widespread penguin species, and, along with the emperor penguin, is the most southerly distributed of all penguins. It is named after Adélie Land, in turn, named for Adèle Dumont d'Urville, who was married to French explorer Jules Dumont d'Urville, who first discovered this penguin in 1840. Adélie penguins obtain their food by both predation and foraging, with a diet of mainly krill and fish.
The first Adélie penguin specimens were collected by crew members of French explorer Jules Dumont d'Urville on his expedition to Antarctica in the late 1830s and early 1840s. Jacques Bernard Hombron and Honoré Jacquinot, two French surgeons who doubled as naturalists on the journey, described the bird for science in 1841, giving it the scientific name Catarrhactes adeliæ. They used specimens collected from an area of the continent which had been named "terre Adélie", French for Adélie Land, itself named for Dumont d'Urville's wife, Adèle. The bird was later placed in several other genera, including Eudyptes, Pygoscelis and the now-defunct genus Dasyrhamphus, and was also later inadvertently redescribed as Pygoscelis brevirostris.
The Adélie penguin is one of three species now assigned to the genus Pygoscelis. DNA evidence suggests the Pygoscelis lineage diverged from that of other penguin species some 38 million years ago, roughly 2 million years after the ancestors of the genus Aptenodytes diverged. Adélie penguins evolved about 19 million years ago, branching from the ancestor of the other two members of the genus (chinstrap and gentoo penguins), both of which evolved some 5 million years later. Although it has no identifiable subspecies, the Adélie penguin has two distinct genetic lineages: one found primarily in the Ross Sea, and the other widespread throughout the Antarctic.
The genus name Pygoscelis is a compound word, composed of the Ancient Greek words pugē, meaning "rump", and skelos, meaning "leg".