Ostriches are large ratite birds in the genus Struthio, a member of the family Struthionidae. They are the tallest and heaviest living birds, growing up to nine feet in height. They first evolved in Africa roughly 21 million years ago, during the early Miocene epoch; between 13 and 5 million years ago the genus had spread into Asia. However, only the African species are still alive today. The Asian species became extinct over time, with the last ones disappearing during the most recent ice age, having lived long enough for humans to encounter them and depict them in art.
There two surviving species of ostrich, one of which has three extant and one extinct subspecies:
- Struthio camelus, the common ostrich:
- S. c. camelus: northern ostrich, found in northern Africa
- S. c. australis: southern ostrich, found in southern Africa
- S. c. massaicus: Masai ostrich, found in eastern Africa
- S. c. syriacus: Arabian ostrich, found on the Arabian Peninsula; extinct during the mid-20th century
- Struthio molybdophanes: Somali or blue-necked ostrich, found on the Horn of Africa
Additionally, there may be as many as eleven extinct species of ostrich.