A new species of Iguanidae Liolaemini lizard from the San Guillermo National Park in western Argentina, is described. The new species is a member of the Liolaemus darwinii complex within the monophyletic boulengeri species group. It is distinguished by its small body size, relatively long tail, low number of scales around midbody, dorsal scales moderately keeled, precloacal pores only in male, bulged patch of enlarged scales on the proximal posterior surface of the thigh in both sexes, dorsal pattern lacking of light vertebral or dorsolateral stripes, antehumeral fold without black pigment in female but greyish in male, a prescapular dark dot dorsal to antehumeral fold in both sexes, and postscapular spot absent. The new species is terrestrial, living in habitats with gravel and sandy soil in an Andean Monte landscape with sparse vegetation, above 2270 meters of altitude.