The scentless plant bug genus Niesthrea Spinola, 1837 (Rhopalinae, Niesthreini) is revised. Fourteen previously described species are diagnosed; Niesthrea ashlocki Froeschner, 1989 and Niesthrea remediana Grillo and Alayo, 1978 (revised synonymy) are synonymized under Niesthrea flava Grillo and Alayo, 1978; Niesthrea parasidae Grillo and Alayo, 1978 is synonymized under Niesthrea sidae (Fabricius, 1794); Niesthrea pictipes casinii Göllner-Scheiding, 1984 is elevated to species status; a neotype is designated for Corizus campoi Porter; and the six new species Niesthrea choprai sp. nov. from Argentina and Peru, Niesthrea conicoloba sp. nov. from Argentina, Niesthrea lateroloba sp. nov. from Peru, Niesthrea parvaloba sp. nov. from Bolivia, Niesthrea rostrata sp. nov. from Colombia and Ecuador, and Niesthrea truncata sp. nov. from Brazil and Colombia are described. A color habitus illustration of N. flava, color digital images of all adults and male genitalia, and an identification key to the 20 currently known species, based primarily on male genitalia, are provided to help distinguish species. Host plants and biogeography are documented.