During an extensive survey of the diatoms of Swedish rivers, a new large Cymbella species, Cymbella amelieana sp. nov., was found. The new species is distinguished by its large valve dimensions, a comparatively higher number of striae in 10 μm and characteristically enlarged, booked central pores. Cymbella peraspera and C. lanceolata, both possess some similar features but can be separated by the differences in the central raphe endings, valve dimensions and apical pore field structure. Other large Cymbella species differ sufficiently by their lower dimensions so as not to be confused with the new species. Cymbella amelieana is a weakly abundant and infrequent species and typically found in circumneutral, oligotrophic rivers.