With more than 407 species of freshwater and brackish water fishes, Gabon is a country rich in ichthyological biodiversity, but its aquatic environments remain poorly explored. We present and describe a new species of Enteromius, adding to the 16 species of Enteromius currently recorded from that country. This new species is distinguished from all other Gabonese Enteromius by the presence of several distinct spots on the dorsal fin in combination with three or four round spots on the flanks. In Africa, it is superficially similar to Enteromius walkeri, and shares with that species an unusual allometry in which the proportional length of the barbels decreases as the fish grows. Nevertheless, one can distinguish these species by vertebral number, maximum standard length, the length of the anterior barbels, the length of the caudal peduncle, and in most specimens, the number of lateral-line and circumpeduncular scales. These two species also inhabit widely separated drainages, with E. walkeri occurring in coastal drainages of Ghana including the Pra and Ankobra Rivers, and the new species occurring in tributaries of the Louetsi and Bibaka rivers of Gabon, which are part of the Ogowe and Nyanga drainages, respectively. Despite extensive collections in those drainages the new species is known from only two localities, suggesting the importance of conservation of its known habitat
