Abstract The taxonomy and nomenclature of the Nearctic species of Enargia Hubner shows a long history of misunderstood species concepts and misapplied names, and the group is revised here. Enargia infumata (Grote, 1874) is a senior synonym of what has been referred to as E. mephisto Franclemont, 1939 for the past 70 years. Late summer moths from boreal areas of Canada and northeastern United previously identified as E. infumata have no available name and are here described as E. fausta sp. n. A lectotype for Orthosia infumata Grote is designated. Adults and genitalia of the three North American species (E. infumata, E. fausta, and E. decolor) are illustrated, and a diagnostic key is provided.