A new freshwater armoured dinoflagellate, Peridiniopsis armebeensis Ten-Hage, K.P.Da et Coute sp. nov., is described from Agneby river, Ivory Coast, West Africa. This new species is illustrated by drawings and light and scanning electron micrographs. The plate formula of P. armebeensis is P-0, X, 4', 6 '', 6c, 4s, 5''', 2''''. Cell is pentagonal to rhombic in ventral view, subcircular in apical view. Cell size ranges are 44-49 mu m long and 37-45 mu m wide. Thecal surface is reticulated and perforated by pores. Small spines are present on the hypotheca. Morphology of P. armebeensis is compared to closely related Peridiniopsis species. An updated identification key to Peridiniopsis. group Penardii, to which belongs P. armeheensis, is provided.