A new crambid, Eoreuma insuastii Solis and Osorio-Mejia, new species, is described from Colombia. The larvae were discovered feeding on young stalks of sugarcane (Saccharum officinarum L.) grown for brown sugar loaf, or “panela.” We provide images of larvae and pupae, as well as damage to sugarcane young stalks for field identification, and describe and illustrate the adults and their genitalia. Only three species of Eoreuma have been previously described from South America; we provide images of the type specimens, their labels, and genitalia. The new species described herein is most like E. donzella Schaus, which was described from Brazil. The other two species are E. paranella Schaus and E. morbidellus Dyar; we designate the male syntype of E. morbidellus as the lectotype. The new species is compared to Eoreuma loftini (Dyar), a common pest species of graminaceous crops such as sugarcane and rice (Oryza sativa L.) in Mexico and the United States.