Synodontis abditus, new species, is described from the Ivindo and the Ngounié rivers, respectively a right and a left bank affluent of the Ogooué River (Gabon) in the Lower Guinea (LG) ichthyofaunal province. The new species is readily distinguished from all its congeners from the LG ichthyofaunal province by: the lack of serrations on the anterior side of the dorsal spine; 63-76 mandibular teeth; and 16-28 serrations on the posterior side of the pectoral spine. This discovery illustrates the importance of submitting collections to thorough alpha-taxonomic research in order to screen them for harbouring hidden species richness. The type locality of S. abditus is the stretch of the Loa Loa Rapids on the Ivindo River, which border the Ivindo National Park. In contrast, the other sub-basin where the new species has been found, the Ngounié River, is currently not near to any Protected Area (PA). Nevertheless, the main anthropogenic threats for these sub-basins are deforestation, over-fishing and pollution from nearby towns and iron-ore mining activities. As such, the discovery of yet another Synodontis species, endemic to the LG ichthyofaunal province, further stresses the need and importance for the installation of a well-documented, and extended network of PAs for the effective protection of the Ogooué basin ichthyofauna in particular and its freshwater fauna at large.