A new species of lizard of the genus Mabuya is described from a small island in the Guadeloupe Archipelago: Terre de Bas, Îles de la Petite Terre. Mabuya parviterrae sp. nov. is allied with the other four species of Mabuya from Guadeloupe. However, it differs in scalation, coloration, and (where available) DNA sequence. Of the nine named species in the genus, only M. dominicana (from Dominica), M. desiradae (from La Désirade), nd M. parviterrae sp. nov. have escaped decimation and possible extinction by the Small Indian Mongoose, Urva auropunctata. The latter two species of skinks are critically endangered, being threatened by the Black Rat (Rattus rattus) and degraded habitat that has not recovered from early land use. The Petite Terre Skink probably has one of the smallest distributions of a vertebrate species. The species consists of approximately 50 individuals living primarily in a dry stone wall of less than 500 square meters in extent.