Comparative morphological studies of specimens included in Dioscorea gillettii from Kenya and Ethiopia show differentiation between a northern group of populations in Sidamo and Bale Provinces in Ethiopia and near Moyale in northern Kenya and a southern group found in Kitui and Meru Districts of Kenya. Thus the southern element is described as a new species. The two species also differ in their pollen morphology. An illustration, distribution map, and a conservation status assessment are provided for D. kituiensis, and its mode of speciation is discussed.