The species of the genus Tachinus (Staphylinidae: Tachyporinae) of North and Central America are revised. Forty-four species are recognized, of which eight are described as new; eight species names are placed in synonymy. The subgenera Drymoporus Thomson and Porodrymus Rey are placed in synonymy with Tachinus and the genus is divided into 17 species groups based on an examination of both the Nearctic and the Palearctic fauna. The distribution of each species is mapped and the male genitalia, the male and female eighth abdominal sternites and tergites, and the male seventh sternite are illustrated for every species. A neotype is designated for T. fumipennis Say, and lectotypes are designated for all the North and Central American species of Tachinus described by Gravenhorst, Erichson, Mäklin, Horn, and Sharp. Diagnostic keys for males and females are included. A brief discussion of the nomenclatural history of the genus, of collecting techniques, and of the major diagnostic characters is included.