Acaena rorida is a species of mat-forming perennial plant known only from grassy uplands on the Mangaohane Plateau in the northwestern part of the Ruahine Range on North Island, New Zealand. Within its range, this plant occurs in areas with moist, stable soils such as in hollows in tussocklands and the floors of ravines. It can be distinguished from its closest congeners by the purple or dull green (rather than bright green) foliage and the sessile fruits which are often hidden among the leaves rather than being borne above. Flowering occurs in December and January with fruit being produced in February.