We describe and formally name a species of bonneted bat (genus Eumops), which is a member of the E. glaucinus complex. Closely related species are E. glaucinus, E. ferox, and E. floridanus. The conceptual basis for the description of this species is the Genetic Species Concept with speciation by the Bateson-Dobzhanzky-Muller model. The new species is distinguished from all other species of bats by its unique karyotype (2N = 38, FN = 54), sequence of the mitochondrial cytochrome-b gene, and genetic markers revealed through analysis of Amplified Fragment Length Polymorphisms. The series from the type locality (Ecuador, Guayas) is comprised of seven specimens. Morphologically, the new species is smaller than E. floridanus and E. glaucinus, but is indistinguishable from E. ferox. The new species is significantly smaller in size than E. glaucinus in six out of eight measurements and is distinguishable from E. glaucinus based on length of maxillary toothrow and zygomatic breadth. The geographic range of E. wilsoni, as currently documented, is the dry forests of southwestern Ecuador and adjacent northwestern Peru. We propose the common name for this species be Wilson's bonneted bat.