Geographical region : plains, prairie, North Dakota,southern part of Saskatchawan
Lived normally in plains-tipois
Language group : siouan
Atsina (Blackfoot: at-se'na, said to mean 'gut people; Ań`ni-nena, under Arapaho).
A detached branch of the Arapaho, at one time associated with the Blackfeet, but now with the Assiniboin under Ft. Belknap agency, Montana, where in 1904 they numbered 535, steadily decreasing.
They called themselves Ań`ninena, said to mean "white clay people", but are known to the other Arapaho as Hit˙nena, 'beggars, or spongers,' whence the tribal sign, commonly but incorrectly rendered "belly people" or "big bellies", the Gros Ventres of the French Canadian and now their popular name.
The Atsina are not prominent in history and in most respects are regarded by the Arapaho proper as inferior to them.
They have been constantly confused with the Hidatsa or Gros Ventres of the Missouri.