A brief history and actual state of knowledge of the tropical liverwort genus Potamolejeunea (Spruce) Lacout. with a list of excluded species are provided. A revision of the species remaining in Potamolejeunea is presented. Examination of type material revealed that the generitype, fl polystachya (Spruce) Steph. is very similar to and congeneric with Trachylejeunea aneogyna (Spruce) Grolle. Therefore, Potamolejeunea is proposed as new synonym of Trachylejeunea (Spruce) Schiffn. For two species of Potamolejeunea that do not fit any other genus (P. uleana and P. polyantha) and for a species previously attributed to Taxilejeunea, (T: tenera) the new genus Neopotamolejeunea is proposed. The species of Neopotamolejeunea occur in Amazonia, where they grow along rivers in periodically flooded lowland rainforests, in Guatemala and Jamaica. The genus is characterised by long robust stems with a pinnate branching pattern and numerous small gametoecial branches on both sides of the stem. Due to its sporophyte features Neopotamolejeunea is included in the tribe Lejeuneae Dumort. and its rather isolated position within this group is discussed. A key to the species, descriptions, illustrations and a distribution map are provided. Trachylejeunea polystachya (Spruce) Steph. and T riparia (Steph.) E. Reiner comb. nov. are also described and illustrated.