North American Indian family of languages that, with the Iroquoian and Caddoan language families, constitutes the Macro-Siouan language phylum. This phylum is, after the Algonquian, the largest native American linguistic phylum north of Mexico. Siouan includes at least five language groups: those of the Gulf Coast region (including Biloxi, Ofo, Tutelo), the upper Missouri River region (including Hidatsa, Crow), the northern plains (including Dakota, or Sioux proper), the central plains (Omaha, Osage, Ponca, Kansa, Quapaw), and the Great Lakes (including Winnebago). The Catawba language of the Carolinas is sometimes classified as a Siouan language.