We describe a new species of Scytalopus tapaculo (Aves: Passeriformes: Rhinocryptidae) from the temperate humid montane forests (2,400-3,200 m) of Junín Department, Peru. This species has a unique song that differs strikingly from that of any known Scytalopus species, consisting of a rapidly repeated series of ascending phrases. Phenotypically, the new species is uniformly blackish in color and small-to-medium in size, most similar to members of the allopatric S. latrans complex. At least six species of Scytalopus occur along an elevational gradient on the eastern slopes of the Andes in Junín; in the vicinity of the type locality, the new species replaces S. femoralis at 2,400-2,500 m, and is replaced by S. acutirostris at 2,900-3,200 m. Throughout its elevational range, the new species is broadly syntopic with the larger S. macropus. This species is currently known from a single river drainage; although it probably occurs more broadly, it is likely a range-restricted species endemic to central Peru.