Wichí Lhamtés Güisnay or Wiznay is a Wichí language. Wichí Lhamtés Güisnay had an estimated 15,000 speakers in 1999 in Argentina. The language is centered in the Pilcomayo River region. Other names for the language include Güisnay, Mataco, Mataco Güisnay, Mataco Pilcomayo, and Wichí Lhamtés. A grammar book has been written for the language.