Elachista arena is a moth of the Elachistidae family that is endemic to Nevada. The length of the forewings is 5.6 millimetres (0.22 in). The forewings are narrow. The ground colour is white, powdered with dark grey scales especially along the costa and the dorsal margin, and with four irregular dark grey stripes. The hindwings are grey and translucent and the underside of the wings is grey.