In 1842, Danish zoologist Johannes Theodor Reinhardt proposed that dodos were ground pigeons, based on studies of a dodo skull he had discovered in the collection of the Natural History Museum of Denmark. The dodo was variously declared a small ostrich, a rail, an albatross, or a vulture, by early scientists.

Skull in the Zoological Museum of Copenhagen, examination of which led to the dodo being classified as a pigeon in 1842 The dodo achieved widespread recognition from its role in the story of Alice's Adventures in Wonderland, and it has since become a fixture in popular culture, often as a symbol of extinction and obsolescence. The extinction of the dodo within less than a century of its discovery called attention to the previously unrecognised problem of human involvement in the disappearance of entire species. Since then, a large amount of subfossil material has been collected on Mauritius, mostly from the Mare aux Songes swamp. Among these is a dried head, the only soft tissue of the dodo that remains today. In the 19th century, research was conducted on a small quantity of remains of four specimens that had been brought to Europe in the early 17th century. Its extinction was not immediately noticed, and some considered it to be a myth. The last widely accepted sighting of a dodo was in 1662. In the following years, the bird was hunted by sailors and invasive species, while its habitat was being destroyed. The first recorded mention of the dodo was by Dutch sailors in 1598. Though the dodo has historically been portrayed as being fat and clumsy, it is now thought to have been well-adapted for its ecosystem. It is presumed that the dodo became flightless because of the ready availability of abundant food sources and a relative absence of predators on Mauritius. One account states its clutch consisted of a single egg. It used gizzard stones to help digest its food, which is thought to have included fruits, and its main habitat is believed to have been the woods in the drier coastal areas of Mauritius.

It has been depicted with brownish-grey plumage, yellow feet, a tuft of tail feathers, a grey, naked head, and a black, yellow, and green beak. Since these portraits vary considerably, and since only some of the illustrations are known to have been drawn from live specimens, the dodos' exact appearance in life remains unresolved, and little is known about its behaviour. The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Subfossil remains show the dodo was about 1 metre (3 ft 3 in) tall and may have weighed 10.6–17.5 kg (23–39 lb) in the wild. A white dodo was once thought to have existed on the nearby island of Réunion, but it is now believed that this assumption was merely confusion based on the also-extinct Réunion ibis and paintings of white dodos. The closest living relative of the dodo is the Nicobar pigeon. The two formed the subfamily Raphinae, a clade of extinct flightless birds that were a part of the family which includes pigeons and doves. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. The dodo ( Raphus cucullatus) is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean.

Bird skeleton sketch