Sioux is a Siouan language spoken by over 30,000 Sioux in the United States and Canada, making it the fifth most spoken Indigenous language in the United States or Canada, behind Navajo, Cree, Inuit languages, and Ojibwe.

The Indigenous languages of the Americas are the languages that were used by the Indigenous peoples of the Americas before the arrival of non-Indigenous peoples. Over a thousand of these languages are still used today, while many more are now extinct. The Indigenous languages of the Americas are not all related to each other; instead, they are classified into a hundred or so language families, as well as a number of extinct languages that are unclassified due to the lack of information on them.