Phymatopsallus Knight, 1964 and related genera endemic to the American Southwest and northern Mexico are revised. Nine new genus-group and 15 new species-group names are proposed. One previously proposed genus-group name and 9 species-group names are treated as junior synonyms. Color digital habitus illustrations of male specimens are provided for all species and females for most species; line drawings of male genitalia are provided for all species; line drawings of female genitalia are provided for one or more representatives of most generic groupings; scanning electron micrographs are used to illustrate a standard set of features for most taxa. Maps are provided to portray the distributions of all Phymatopsallus-group taxa and the outgroup taxon Schaffneropsallus, new genus. A phylogenetic analysis is conducted for 29 ingroup and 3 outgroup taxa. Distributional patterns and host associations are analyzed and discussed.