The first part of a detailed taxonomic study of the butterfly genus Morpho, covering the subgenera Iphimedeia and Schwartzia. Each sub-genus is presented according to the same plan: diagnosis, indications of the type species, list of taxa solutions considered here as species and a critical analysis underlining the difficulties posed by these taxa and presenting the solutions adopted. Each species is then studied in detail. Indications available about geographical distribution are provided as precisely as possible and illustrated by maps which distinguish, should the occasion demand it, the different sub-species admitted in the systematic study. Wherever possible, indications on flight periods have been provided.