ABSTRACT. – Monogenean species assigned to Synodontella Dossou & Euzet 1993 infect siluriform fish belonging to Synodontis Cuvier, 1816. A parasitological survey of Synodontis rebeli Holly, 1926 and Synodontis obesus Boulenger, 1898 from the River Sanaga and Lake Ossa (South Cameroon) revealed the presence of three species of Synodontella of which one, Synodontella melanoptera Dossou & Euzet 1993, was already described. The other two Monogenea identified, based on the size of sclerotized parts of the haptor and the male copulatory complex, are new to science and named Synodontella apertipenis n. sp. and Synodontella sanagaensis n. sp. Both species only found on the gill filaments of S. rebeli are considered oioxenous, while Synodontella melanoptera parasitizing the gill filaments of two different host species of the same genus is mesostenoxenous. This study also reveals the enlargement of the host spectrum of Synodontella melanoptera.