Synanthedon namdoelegans sp. nov., a new clearwing moth, is described from southern South Korea. It is closely related to Synanthedon soffneri ?patenka, 1983, Synanthedon bastak Gorbunov & Koshkin, 2023, and Synanthedon velox Fixsen, 1887, but can be distinguished by differences in the forewing’s black band, the hindwing’s discoidal vein spot, and male genitalia. The female and larval stages are unknown. DNA barcode sequences show minimal variation (0.46%) within S. namdoelegans, with divergence from other Synanthedon species ranging from 1.98% to 12.46%. Phylogenetic analysis shows separation of S. namdoelegans from its closest relatives, Synanthedon fulvipes Harris, 1839 and Synanthedon culiciformis Linnaeus, 1758. These differences provide clear morphological and molecular separation from other Synanthedon species.