A new species of Bryophryne from southern Peru (Cusco Region) is described. Specimens were found in the leaf litter of cloud forest at elevations of 2350-3215 m. The new species has a maximum snout-vent length of 21.9 mm in adult females, 18.9 mm in adult males and is the smallest species of the genus. It lacks a tympanum and dentigerous processes of vomers, has dorsolateral folds, and males without vocal slits and without nuptial pads. The new species is most similar to B. bustamantei but differs in being smaller, having discontinuous dorsolateral folds, the males lacking vocal slits, and an overall darker ventral coloration. Bryophryne contains three species all of which lack a tympanum. The deep valley of the Río Apurímac as a distributional barrier separating Phynopus from Bryophryne is discussed. Copyright © 2008 Magnolia Press.