Leptogomphus sauteri Ris, 1912, is a species endemic to Taiwan and is currently treated as having two subspecies, L. sauteri sauteri and L. sauteri formosanus Oguma, 1926. However, the two subspecies are difficult to distinguish due to morphological similarity or overlap. In this study, morphological and molecular methods are used to reassess the taxonomic status of the two subspecies. It can be confirmed that three morphological characters, namely body size, coloration, and the male accessory genitalia, and two molecular genetic markers, namely nuclear ITS1 and mitochondrial COI segments, fail to discriminate between the two subspecies. These results suggest that the splitting of L. sauteri into two subspecies is not justified. Therefore, the taxon L. formosanus is treated as a junior synonym of L. sauteri.