A new species of freshwater diaptomid copepod, Skistodiaptomus ozarkensis, is described from lakes, ponds, and flooded fields in the Ozark Plateau region of the U.S.A. A general description with illustrations of the body and appendages of the adult male and female S. ozarkensis is presented. The new species seems to be quite closely related to S. reighardi (Marsh, 1895) and was reported previously as this species. Several morphological characters are identified that separate these two species from each other as well as from S. oregonensis (Lilljeborg, 1889). Among these characters, the shape of segment 2 of the exopod of the male left fifth leg most clearly separates the three species.