The genus Urosigalphus Ashmead is divided into 5 new subgenera (Microurosigalphus, Neourosigalphus, Urosigalphus, Bruchiurosigalphus, and Paraurosigalphus). Keys to the subgenera and to species of each subgenus are presented along with detailed descriptions of each subgenus and of each species. This revision includes 36 species of the United States and Canada of which 21 are new. The known biology and distribution of each species is given. The species are internal parasites of weevil larvae of the families Bruchidae and Curculionidae.