Based on fieldwork conducted in northwestern Argentina for the Planetary Biodiversity Inventory project, and from the study of several specimens of entomological collections from other Neotropical countries—in particular Chile and Argentina—new taxa are described, and additional nomenclatural and distributional notes are provided for some Neotropical Orthotylini taxa. The male genitalia of Biobiocoris setosus Carvalho, 1985 are illustrated, and a diagnosis is proposed for this monotypic genus. New distributional information for B. setosus is provided, which is newly recorded from Argentina. Chileria andina, sp. nov., is described from Argentina. Host-plant data are given for the new species. Conostethus pamparum Berg, 1883 is transferred to Chileria, and Saileria chilena Carvalho and Carpintero, 1991, is proposed as junior synonym of Chileria pamparum, comb. nov. Detailed male genitalia drawings are provided, including genital capsule and phallotheca, for all the known species of Chileria. Based on these changes, a diagnosis of Chileria is provided as well as a key to all the species. Female genitalic structures of Hadronemella argentina (Carvalho and Wallerstein, 1978) are described and depicted, and new distributional information is provided. Hyporhinocoris tomentosus Reuter, 1909, is regarded as a junior synonym of Hyporhinocoris fratruelis (Berg, 1879). Hyporhinocoris is thus a monotypic genus with widespread distribution in Argentina associated with Larrea spp. (Zygophyllaceae). Orthotylus chullan, sp. nov., O. kakan, sp. nov., and O. kikin, sp. nov., are described from Chile. Male and female genitalic structures are compared with the most similar described species, O. chilensis Carvalho and Fontes, 1973. A diagnosis is proposed for O. tafoensis Kerzhner and Schuh, 1995, and its male genitalia illustrated. New distributional and host-plant information is provided for O. chilensis and O. tafoensis. Platyscytus youngi, comb. nov. (Phylinae) is proposed for Saileria youngi Carvalho, 1953, and thus removed from the Orthotylinae. A diagnosis for Saileria bella (Van Duzee, 1916), the type species of Saileria, is provided and its male genitalia illustrated. Digital dorsal habitus photographs are provided for all the species treated, and distribution maps are provided for the South American taxa. Scanning electron micrographs of selected structures and illustrations of male genitalia are presen