The copper pheasant (Syrmaticus soemmerringii), also known as Soemmerring's pheasant or yamadori (ヤマドリ), is a pheasant endemic to the Japanese archipelago. The scientific name commemorates the German scientist Samuel Thomas von Sömmerring. It is the official bird of multiple Japanese prefectures, cities, and towns. It was commonly hunted for sport throughout the 20th century.

Its population has been in consistent decline since the 1970s due to factors including habitat destruction and predation, but the most widely cited cause is overhunting.

The copper pheasant was described in 1830 by Coenraad Temmerick as Phasianus soemmerringii. It was named for the German scientist Samuel Thomas von Sömmerring, while the subspecies S. s. ijimae is named for Japanese zoologist Isao Ijima. It was reclassified into the Syrmaticus genus in 1914 by William Beebe, despite the differences between the males, because he saw a high number of similarities between females of the genus. However, based on the reports of interbreeding between the copper pheasant and the green pheasant (Phasianus versicolor) in Nobusuke Takatsukasa's 1943 pamphlet, Studies of the Galli of Nippon, the Ornithological Society of Japan moved the bird back into the Phasianus genus. In the same book, Takatsukasa also split the copper pheasant into two species and eliminated all subspecies. Those, as well as other taxonomic changes he proposed, were termed by a United States Fish and Wildlife Service report as "not in accordance with sound systematic practice". The copper pheasant is sometimes still referred to as Phasianus soemmerringii in Japanese literature.

There are five recognized subspecies of copper pheasant:

Both S. s. ijimae and S. s. scintillans were initially described as distinct species.

Pleistocene-era Syrmaticus fossils in Japan have been classified as S. soemmerringii, but this identification is disputed.

It is a large pheasant with a rich coppery chestnut plumage, yellowish bill, brown iris, and red facial skin. The female is a brown bird with greyish brown upperparts and buff barred dark brown below. The male has short spurs on its grey legs, while the female has none. Males are between 87.5 centimetres (34.4 in) and 136 centimetres (54 in) long, including the tail, while the female is between 51 centimetres (20 in) and 54 centimetres (21 in) (subspecies scintillating copper pheasant, scintillans). Juveniles have similar plumage to the females. The plumage of the chicks is, overall, chestnut, with some darker patches of brown on the back of the neck and cream-coloured feathers on the face. Darker stripes of cream and dark brown run along their face and neck.

The copper pheasant is distributed in and endemic to the hill and mountain forests of the Honshū, Kyūshū, and Shikoku islands at elevations of up to 1,800 metres (1.1 mi). It typically confines itself to deciduous forest floors with extensive vegetation. However, members of the species also lives in conifer forests. They often nest on the edges of grasslands. It naturally occurs only south of the Blakiston's Line, and this species' distribution was originally cited as evidence for the line's existence.