We collected 423 species of diurnal butterflies (Rhopalocera) during 250 days of observations from March 1997 through January 2000 in the region of Calakmul, Campeche, Mexico. We present a list of 428 species recorded for Calakmul. This is the first reported list of butterflies for the state of Campeche, and it includes 290 new records for the state, 374 new records for Calakmul, and 1 new record for Mexico: Monca telata. Museum records were found for 5 additional species: Caria melino, Cissia labe, Tmolus echion, Emesis lupina lupina, and Calephelis azteca. The accumulation curve of species estimates that 457 species should be present in Calakmul, which suggests the list presented is 93% complete. We found that medium, tropical, semi-evergreen forest is the richest (371 species); more than a quarter of the butterflies of the Calakmul region were found exclusively in this forest. We also found the southern area slightly more abundant in species (82%) than the northern area (79%). Additionally, a comparison was made of the list generated for Campeche to lists from previous studies for Quintana Roo, Tikal-Guatemala National Park, and Belize. The comparison shows that 70%, 58%, and 54% of the butterfly species in Calakmul also are found in Tikal, Quintana Roo, and Belize, respectively.