Guaicuruan (Guaykuruan, Waikurúan, Guaycuruano, Guaikurú, Guaicuru, Guaycuruana) is a language family spoken in northern Argentina, western Paraguay, and Brazil (Mato Grosso do Sul).
For the most part, the Guaycuruans lived in the Gran Chaco and were nomadic and warlike, until finally subdued by the various countries of the region in the 19th century.
Jorge A. Suárez includes Guaicuruan with Charruan in a hypothetical Waikuru-Charrúa stock.
Morris Swadesh includes Guaicuruan along with Matacoan, Charruan, and Mascoian within his Macro-Mapuche stock.
The similarities with the Mbayá language may be due to borrowing rather than a familial relationship.