Here we present a revision of the Neotropical genus Eurrhacus Waterhouse, 1879 that is placed in Eurrhacini tribe, strongly related to Calopterini, being the only genus from these tribes or even among exclusive Neotropical lycids known so far to present reduced or absent parameres. Six species are placed in the genus, two of them, E. tristis (Waterhouse, 1878) and E. pectinicornis (Gorham, 1881), are redescribed, and four species are proposed as new to science: E. amazonicus sp. nov., E. paraensis sp. nov., E. ecuadorensis, sp. nov., and E. kaboureki sp. nov.