The addax (Addax nasomaculatus), also known as the white antelope and the screwhorn antelope, is an antelope native to the Sahara Desert. The only member of the genus Addax, it was first described scientifically by Henri de Blainville in 1816. As suggested by its alternative name, the addax has spiral horns that are 55 to 80 cm (22 to 31 in) long in females and 70 to 85 cm (28 to 33 in) in males. In the winter, its coat is greyish-brown with white hindquarters and legs, and long, brown hair on the head, neck, and shoulders; in the summer, the coat turns almost completely white or sandy blonde. Males stand from 105 to 115 cm (41 to 45 in) at the shoulder, with females at 95 to 110 cm (37 to 43 in). They are sexually dimorphic, as the females are smaller than the males.

The addax lives in arid regions, semideserts and sandy and stony deserts in North Africa. It mainly eats grasses and leaves of shrubs, leguminous herbs and bushes. It can live without water for long periods of time. Addax form herds of five to 20 members, consisting of both males and females. The herd is usually led by one dominant male. Breeding season is at its peak during winter and early spring.

The addax is listed as critically endangered on the IUCN Red List. It was once abundant, but is currently restricted to Chad, Mauritania and Niger. It is threatened by unregulated hunting and is locally extinct in Western Sahara, Algeria, Libya, Egypt and Sudan.

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