A new species of the Iguanian genus Liolaemus, member of the montanus series, is described. The species inhabits altitudes above 4000 meters and is endemic to the Provincial Reserves of Laguna Brava, province of La Rioja, and San Guillermo, province of San Juan, areas located in the Andes mountains of Argentina. Liolaemus sp. nov. has a medium-sized body (maximum SVL = 76.9 mm) with tail subequal in length to the SVL; unkeeled, juxtaposed dorsal scales, in high number around midbody (86–106); precloacal pores in males (4–7), mostly absent in females or in very low number (up to 2 pores); head and body strongly melanic; evident sexual dichromatism, and a distinctive color pattern. Liolaemus sp. nov. lives geographically close but in allopatry to L. andinus, L. eleodori and L. vallecurensis, all species of the montanus series, morphologically alike and probably phylogenetically related to the new species.