Mormyrid fishes comprise the largest endemic family of freshwater fishes in Africa. With more than 200 species, this fish family is widely distributed in the continent except for the Cape region and the 15 Maghreb. Characteristic for these fishes is the presence of an electric organ, which is located in the caudal peduncle. Amongst these elephant-fishes, Pollimyrus isidori has a widespread distribution in Africa and is currently divided into three subspecies: the nominate subspecies Pollimyrus isidori isidori (Valenciennes, 1846) occurs in the Nile basin and ranges widely in the Nilo-Sudan and Upper-Guinea ichthyofaunal provinces, while the other two subspecies P. isidori osborni (Nichols & Griscom, 1917) and P. isidori fasciaticeps (Boulenger, 1920) show an overlapping distribution in the Congo ichthyofaunal province. We reviewed and analysed the different populations of P. isidori. A Principal Component Analysis on 27 log-transformed measurements clearly revealed the presence of two groups with no overlap. One group consists of specimens from the Congo River basin, and contains the holotypes of P. isidori osborni and P. isidori fasciaticeps. The second group is associated with specimens from the Nile River system and the different river basins of West Africa. It includes the type specimens of P. isidori isidori. Both groups can be separated using (a combination of) the following characters: eye-diameter, inter-orbital width and anal-fin length. We also noted differences in color-pattern between both groups. A closer examination of the specimens from the Congo ichthyofaunal province could not reveal any difference between the populations. Considering the non-overlapping distributions and the various diagnostic differences between Nilo-sudanic and Congo basin specimens, both areas are believed to contain a single valid species without subspecies, P. isidori and P. osborni respectively.