We describe a new species of frog from the eastern slopes of the Andes in central Peru. Pristimantis sira sp. nov. has a distinctive crossing mark on the iris and no tympanum. The new species is closely related to P. antisuyu Catenazzi & Lehr, 2018, P. cruciocularis Lehr, Lundberg, Aguilar & von May, 2006, and P. erythroinguinis Catenazzi & Lehr, 2018, but is easily differentiable by lacking colour blotches on groins. Pristimantis sira sp. nov. inhabits the mountain forests from 1550 to 2200 m a.s.l., inside a national reserve threatened by illegal mining.