The genus Diatraea Guilding is one of the most economically important groups of moths in the Western Hemisphere. The larvae are stem borers that feed on species of Poaceae, or grasses, such as sugarcane, corn, rice, and sorghum, as well as many other native grasses. Interest in this group has risen considerably since sugarcane and other grasses have been utilized and/or investigated as biofuels. This is the first modern study to treat all 41 valid described species. Most type specimens were examined and we provide a checklist with 19 new synonyms. We provide keys for the identification of most species in this genus based on morphology of the male and female genitalia and modern illustrations of male and female genitalia. We also provide an updated table of species distribution by country.