Aristida surperuanensis sp. nov. is described and illustrated. The new species, from southern Moquegua (Peru), differs from A. flaccida in having contracted panicles, spikelets to 1–1.1 cm long and lemmas 5.5–6.5 mm long. The central awn is straight, ascending, 3–6 mm long and lacking a column, the lateral awns are ascending, 1–2.5 mm long and 1/3 as long as the central awns, and the caryopses are fusiform and 4–4.5 (–6) mm long. A key to the species of Aristida in Peru is included and the conservation status of the new species is evaluated.