This review of the ground beetle genus Selenophorus Dejean of the Nearctic Region north of Mexico supplements the taxonomy and biogeography reported in an earlier catalogue on the North American Geadephaga. Eight new species of Selenophorus are described, seven Nearctic and one Neotropical. Selenophorus pararuficollis Messer and Raber, new species in South America and Selenophorus neoruficollis Messer and Raber, new species in southern United States join Neotropical Selenophorus ruficollis (Putzeys) in the previously monobasic S. ruficollis species group of subgenus Selenophorus. Also added to subgenus Selenophorus are Selenophorus undatus Messer and Raber, new species, S. opalinus species group; Selenophorus elytrostictus Messer and Raber, new species, S. striatopunctatus species group; Selenophorus balli Messer and Raber, new species, S. hylacis species group; Selenophorus rileyi Messer and Raber, new species, S. palliatus species group. Added to subgenus Celiamorphus Casey are Selenophorus nonellipticus Messer and Raber, new species, S. ellipticus species group; Selenophorus pumilus Messer and Raber, new species, S. pumilus species group. Thirteen new synonyms are proposed: Selenophorus municeps (Casey) with Selenophorus ellipticus Dejean; Selenophorus adjunctus (Casey), Selenophorus nanulus (Casey), and Selenophorus subtropicus (Casey) with Selenophorus granarius Dejean; Selenophorus elongatus (LeConte) with Selenophorus hylacis (Say); Selenophorus scolopaceus Casey with Selenophorus aeneopiceus Casey; Selenophorus cupreolus Casey, Selenophorus houstoni Casey, Selenophorus implicans Casey, and Selenophorus riparius Casey with Selenophorus pedicularius Casey; Selenophorus otiosus Casey with Selenophorus planipennis LeConte; Selenophorus laesus (LeConte) with Selenophorus palliatus (Fabricius); Selenophorus famulus Casey with Selenophorus aequinoctialis Dejean. Selenophorus schaefferi Csiki, revised status is removed from synonymy with Amblygnathus subtinctus (LeConte) and restored to species status. Discoderus discoderoides (Schaeffer), new combination is transferred from genus Selenophorus. The previous transfer from genus Selenophorus to Athrostictus punctatulus (Putzeys) is clarified. A key identifies the 15 species groups and the 37 species of adult Nearctic Selenophorus. The 24 species of Selenophorus reported for Texas make it the most species-rich state. The four kinds of sexual dimorphism in Selenophorus are found to be taxonomically useful character states. Several new state records of the United States and new country records of the New World are reported. New to the USA are one West Indian species and five Mexican species. Among the latter group is the southwestern species S. aequinoctialis, which is distinguished from the similar S. palliatus of the eastern USA. Eight strictly Neotropical species are compared to their similar Nearctic counterparts. Figures include habitus photographs of 40 species and line drawings of male genitalia for the new species.