The staphylinid genus Philothalpus is revised. The species of Allostenopsis Bernhauer and Eugastus Sharp are shown to be congeneric with Philothalpus fervidus (the type species of Philothalpus), and consequently, Allostenopsis Bernhauer and Eugastus Sharp are placed as junior synonyms of Philothalpus Kraatz. Allostenopsis kraatzi Bernhauer is shown to be a junior synonym of A. antennaria Bernhauer. Seventeen species are described as new: P. asymmetros sp. n. from Ecuador, P. bilobus sp. n. from French Guiana, Guyana and Suriname, P. brooksi sp. n. from Colombia, Ecuador and Panama, P. chloropennis sp. n. from Panama, P. chotaenus sp. n. from Colombia, P. ecuadorensis sp. n. from Ecuador, P. falini sp. n. from Costa Rica and Nicaragua, P. loksos sp. n. from Colombia, Ecuador and Peru, P. mauroprasinus sp. n. from Guyana, P. nitidus sp. n. from Brazil, P. osanus sp. n. from Costa Rica, P. pecki sp. n. from Brazil and Peru, P. porphyros sp. n. from Ecuador, P. portokalis sp. n. from Ecuador, P. rufus sp. n. from Panama, P. rugosus sp. n. from Panama, and P. stravos sp. n. from Ecuador and Peru. Lectotypes are designated for Eugastus mundus Sharp, Philonthus fervidus Erichson, and Stenopsis kraatzi Bernhauer. Distributional maps, a key and illustrations of structural features including aedeagi are provided for the identification of the known species. Phylogenetic analysis of three outgroup and 21 ingroup taxa based on 43 characters resulted in three equally most parsimonious trees (CI = 0.48, RI = 0.66). The monophyly of Philothalpus is supported by high Bremer support and bootstrap values.