Elachista perniva is a moth of the Elachistidae family. It is found in North America in Saskatchewan, Colorado and Wyoming. The length of the forewings is 4.8–5.5 millimetres (0.19–0.22 in). The costa in the basal fifth of the forewing is grey. The wing is otherwise snow-white. The hindwing varies in colour from light grey to dark brownish grey. The underside of the wings is dark grey.