A new genus, Pachacutia n. gen., of large, rare Andean ithomiine butterflies is described and characterized, containing four species. Two species and their constituent subspecies and synonyms (Ithomia cleomella Hewitson, Ithomia mantura Hewitson, Ithomia honrathi Srnka, and Dircenna barrettii Dannatt) are transferred to Pachacutia from Godyris Boisduval (n. comb.). Two additional species are described from southern Ecuador (Pachacutia baroni n. sp.) and Bolivia (Pachacutia germaini n. sp.), and a new subspecies, Pachacutia mantura joroni n. ssp., is described from Peru. Pachacutia is a member of a clade containing otherwise small, often abundant lowland forest ithomiines, including Mcclungia R.M. Fox, Brevioleria Lamas, and some species of Hypoleria Godman & Salvin. A comparative phylogenetic analysis showed Pachacutia species to be related as follows: (baroni + (mantura + (cleomella + germaini))). A key for identification of all taxa, and illustrations of male and female genitalia for all species and adult specimens of all taxa, are presented, and the taxonomy and natural history of all taxa are discussed. © 2007 Entomological Society of America.