The Cheyenne (/ʃaɪˈæn/ shy-AN) are one of the groups of indigenous people of the Great Plains and their language is of the Algonquian language family. The Cheyenne comprise two Native American groups, the Só'taeo'o or Só'taétaneo'o (more commonly spelled as Suhtai or Sutaio) and the Tsétsêhéstâhese (also spelled Tsitsistas). These tribes merged in the early 19th century. Today, the Cheyenne people are split into two federally recognized groups: Southern Cheyenne, who are enrolled in the Cheyenne and Arapaho Tribes in Oklahoma, and the Northern Cheyenne, who are enrolled in the Northern Cheyenne Tribe of the Northern Cheyenne Indian Reservation in Montana.
The Cheyenne lived in the area of what is now Minnesota at the time of their first contact with the Europeans. They were at times allied with the Lakota and Arapaho. They migrated west across the Mississippi River and into North and South Dakota in the early 18th century. They adopted the horse culture and through ritual ceremonies and structure, developed a more centralized authority than other Plains Indians of the 19th century. Having settled the Black Hills of South Dakota and the Powder River Country of present-day Montana, they introduced the horse culture to Lakota bands about 1730. Allied with the Arapaho, the Cheyenne pushed the Kiowa to the Southern Plains. In turn, they were pushed west by the more numerous Lakota.
The Cheyenne Nation or Tsêhéstáno was at one time composed of ten bands that spread across the Great Plains from southern Colorado to the Black Hills in South Dakota. When they gathered, the bands' leaders would meet in formal council. They performed an annual Arrow Renewal ceremony and Sun Dance. They fought their traditional enemies, the Crow and later (1856–79) the United States Army forces. In the mid-19th century, the bands began to split, with some bands choosing to remain near the Black Hills, while others chose to remain near the Platte Rivers of central Colorado.
The Northern Cheyenne, known in Cheyenne either as Notameohmésêhese, meaning "Northern Eaters" or simply as Ohmésêhese meaning "Eaters", live in southeastern Montana on the Northern Cheyenne Indian Reservation. Tribal enrollment figures, as of late 2014, indicate that there are approximately 10,840 members, of which about 4,939 reside on the reservation. Approximately 91% of the population are Native Americans (full or part race), with 72.8% identifying themselves as Cheyenne. Slightly more than one quarter of the population five years or older spoke a language other than English.
The Southern Cheyenne, known in Cheyenne as Heévâhetaneo'o meaning "Roped People", together with the Southern Arapaho, form the Cheyenne and Arapaho Tribes, in western Oklahoma. Their combined population is 12,130, as of 2008. In 2003, approximately 8,000 of these identified themselves as Cheyenne, although with continuing intermarriage it has become increasingly difficult to separate the tribes.