Based on morphological evidence, we describe a new species of agamid lizard of the genus Calotes that is restricted to a single site on the northern face of the Knuckles massif (∼1000 m above sea level) of Sri Lanka. The genus Calotes consists of eight species in Sri Lanka, six of which appear to form an endemic radiation. The new species, Calotes manamendrai, most closely resembles Calotes liolepis Boulenger, 1885, which is widely distributed in mid-elevations in the central highlands, lowland rain forests, and a few isolated moist forests in the dry zone of Sri Lanka. Females of Calotes manamendrai sp. nov. differ from the females of Calotes liolepis in having nonenlarged pectoral scales; keeled dorsal scales on the body; smaller midgular scales than the rest of the throat scales; brown color, seven distinct stripes each side on gular area; black color shoulder pit; and upper arm with carinate ventral scales. Finally, we provide a complete redescription for Calotes liolepis based on the adult female syntypes.