Abstract Seven species of Marimatha Walker are examined, five of which occur in North America. In addition to the existing species M. nigrofimbria (Guenee), M. tripuncta (Moschler) is reported from North America for the first time and three new species are described from southwestern North America: M. piscimala, M. squala, and M. quadrata. Marimatha alboflava (Walker), M. botyoides (Guenee), and M. dinumeratalis (Walker) are discussed in terms of the generic name Marimatha, and M. aurifera (Walker) is discussed in relation to the identity of M. tripuncta. A generic diagnosis, key to species, descriptions, and illustrations of adults and genitalia are included. A new genus and species is proposed for a species currently placed as an undescribed species of Marimatha, but tympanal and genital characters and mtDNA suggest an association with the subfamily Noctuinae, tribe Elaphriini.