The genus Myotis is a diverse group of vespertilionid bats found on nearly every continent. One clade in this group, the subgenus Chrysopteron, is characterized by reddish to yellowish fur and, in some cases, visually striking dichromatic wing pigmentation. Here, we describe a new dichromatic species of Myotis (Chrysopteron) from the Nimba Mountains in Guinea. The new species is superficially similar to Myotis welwitschii, but phylogenetic analyses based on cytochrome b data indicated that it is actually more closely related to M. tricolor. Discovery of this new taxon increases the number of Myotis species known from mainland Africa to 11 species, although patterns of molecular divergence suggest that cryptic species in the Chrysopteron clade remain to be described. This discovery also highlights the critical importance of the Nimba Mountains as a center of bat diversity and endemism in sub-Saharan Africa.