Group of American Indian languages belonging to the Macro-Siouan language family. Siouan is the dominant language group of the Great Plains region of the USA and Canada. It has two branches: Siouan Proper and Catawba. Siouan Proper includes the languages of the Mandan, Crow, and Hocák (or Winnebago); the Dakota, Nakota, and Lakota dialects spoken by the Sioux and related dialects of the Assiniboine and Stoney peoples of Canada; and the nearly extinct Dhegiha languages of the Kaw, Osage, Ponca, Omaha, and Quapaw. The Catawba branch contains only the almost extinct language of the Catawba people.