The Great Bustard (Otis tarda) is in the bustard family, the only member of the genus Otis. It breeds in southern and central Europe, where it is the largest species of bird, and across temperate Asia. European populations are mainly resident, but Asian birds move further south in winter.

The male of this huge bird is possibly the heaviest living flying animal, alongside the similarly sized Kori Bustard. A male is typically 90–105 cm (35–41 in) tall, with a length of around 105 cm (41 in) and has a 2.1–2.7 m (6.9–8.9 ft) wingspan. The male can range in weight from 5.8 to 18 kg (13 to 40 lb), with an average of 13.5 kg (30 lb). The heaviest verified specimen was about 21 kg (46 lb); larger specimens have been reported but remain unverified. An adult male is brown above and white below, with a long grey neck and head. The breast and lower neck sides are chestnut. In the breeding season, the male has long white neck bristles. In flight, the long wings show large areas of white.

The female is about a third smaller in linear dimensions, typically measuring 75 to 85 cm (30 to 33 in) in height, about 75 cm (2.46 ft) in length and 180 cm (5.9 ft) across the wings. At an average of 4.4 kg (9.7 lb), the females are one-third the weight of the male. Overall, the female's weight can range from 3.3 to 8 kg (7.3 to 18 lb). Perhaps because of this physical sexual dimorphism, there is a skewed sex ratio of about 1.5:1 female to male. The breast and neck of the female are buff. Both sexes are usually silent. Immature birds resemble the female.