The present new species, Cobitis koreensis is very common in the upper and middle freshwater regions of the rivers flowing into the Yellow Sea. This fishes live on the clear, stony bottom. Till now this species has been regarded as a variation of C. taenia by all the ichthyologists in Korea. Since 1972, the author has collected a large number of specimens in the rivers of the whole country and compaired them. From the viewpoint of the secondary sexual characters which play an important role in the taxonomy of this genus, a new fact has been found that there is a distinct discontinuity not only between the present species and C. taenia, but also between its allied species. The author therefore proposes herein to describe it as a new species.