The A. cornuta, A. spinifer, A. cribratifrons, and A. monstrata species groups sensu Jeannel (1962) of the species-rich genus Achilia Reitter, 1890 are revised. Of the ten taxa placed in these four groups of species, two belong to different groups and will be treated in a subsequent part of our revision of Achilia (i.e. A. caneloi Franz, 1996 and A. simpsoni Franz, 1996 with the A. cosmoptera and the A. bicornis groups, respectively), two names are placed in synonymy – A. parangulifrons Franz, 1996 = A. lobifera Jeannel, 1962 syn. nov., and A. monstrata chilota Jeannel, 1962 = Achilia monstrata (Reitter, 1885) syn. nov. – and A. pseudangulifrons Franz, 1996 is considered as a species inquirenda. The remaining five species are redescribed, and the new species Achilia pullastra n. sp., attributed to the A. spinifer group, and Achilia pugila n. sp., attributed to the A. cribratifrons group, are described. For all these species the distribution is detailed and mapped, and habitat/collecting data are summarized.