Although traditionally placed in the genus Pipistrellus, studies since the mid-1900s have shown that the western pipistrelle (P. hesperus) and eastern pipistrelle (P. subflavus), the only 2 representatives of Pipistrellus-like bats in the Western Hemisphere, do not share a most recent common ancestry with true Pipistrellus or each other. More than 20 years ago, authors recommended taxonomic revision for the American pipistrelles by placing subflavus in a separate genus called Perimyotis, and hesperus in a another separate genus called “Parastrellus.” Recently, a comprehensive study of the molecular phylogenetics of vespertilionid bats affirmed these suggested revisions. However, the name “Parastrellus” is currently unavailable according to the International Code of Zoological Nomenclature because no formal description of the genus has been provided. In this study, we provide additional morphological and genetic data demonstrating the marked divergence among hesperus, subflavus, Pipistrellus, and other Pipistrellus-like genera, and provide a formal description of a new generic name for the nominal species P. hesperus.