This study describes a new species of lizard of the genus Liolaemus (L. lonquimayensis), without precloacal pores, associated with the lava flows of the Lonquimay volcano in the Región de la Araucanía, Chile. This species belongs to the elongatus clade, and is a sister lineage of L. elongatus. L. lonquimayensis differs from its sister species, L. elongatus, in the total absence of precloacal pores, smaller maximum SVL (69.7 mm in L. lonquimayensis and 91.0 mm in L. elongatus), greater number of midline scales (88 in L. lonquimayensis and 77 in L. elongatus), body color light grey to black in L. lonquimayensis and light to dark brown in L. elongates. L. lonquimayensis has an black occipital band formed by small black lines arranged horizontally flanked by two lighter dorsal longitudinal bands, more separated towards the tail, forming incomplete rings. Finally, a combination of genetic, meristic and morphological characters distinguishes L. lonquimayensis from the other species of the elongatus clade.