Cyphocharax biocellatus, a species of curimatid characiform apparently endemic to the Marowijne River/Fleuve Maroni system in Suriname and French Guiana, and the Maim River basin in French Guiana is described as new. The new species is diagnosed from congeners based on meristic and morphometric features and details of pigmentation of the body and dorsal and caudal fins. The description of the new species brings the total number of Cyphocharax species in the drainages overlying the Guiana Shield to 14, with eight species occurring in the northern-flowing river systems of the Guianas. As such, the Guianas demonstrate the highest species-level diversity within Cyphocharax among comparably-sized areas within the range of the genus. The pronounced diversity of the genus Cyphocharax and the family Curimatidae at the level of the Maroni basin, the Guianas and the rivers systems draining the Guiana Shield is discussed.