Viola guaxarensis M. Marrero, Docoito Díaz & Martín Esquivel, sp. nov., belonging to V. sect. Melanium Ging. (Violaceae), is described and illustrated. It is a small chamaephyte currently known in only two localities within the high-mountain zone of Tenerife, Canary Islands. Data on aspects of its morphology, ecology, rarity and conservation status are provided, as well as the differences between this new taxon and the other two species from the Canary Island high-mountain habitats, V. cheiranthifolia Humb. & Bonpl. and V. palmensis Webb & Berthel., which are presumed to be the closest relatives.