Elachista ossuaria is a moth of the Elachistidae family that is found in Alberta, Yukon, Arizona, Colorado, Montana and Wyoming. The length of the forewings is 4.9–6 millimetres (0.19–0.24 in). The forewing costa in the basal 1/6 is grey. The ground colour is unicolorous yellowish-white. The hindwings are light grey, while the underside of the wings is grey.