Elachista argentosa is a moth of the Elachistidae family. It is found in the United States, where it has been recorded from Ohio and Maine. The wingspan is 7-8 mm. The forewings are almost black with faint golden brown reflections. The markings are metallic silvery, with golden and bluish reflections. The base of the wing is silvery. The hind wings are grayish brown, becoming bluish along the costa near the base. Adults have been recorded on wing from May to August.