The primary objective for this study was to redefine the species delimitation among the different morphological entities of Syringa native to Korea. Particular attention was focused on S. wolfii Schneider, S. patula (Palibin) Nakai and S. reticulata (Blume) Hara because of the high degree of morphological intergradation and its inconsistent circumscription across the various systematic treatments. The proportion of length to width of leaf, the proportion of corolla tube to length of calyx, the proportion of corolla tube to length of corolla lobe, the proportion of corolla tube to length of stamen, and length of fruit were important characters that permit the differentiation of examined taxa. The close morphological association of inflorescence type, presence of hair on pedicel, calyx and length of corolla indicated that S. formosissima Nakai, S. formosissima var. hirsuta (Nakai) Nakai, S. robusta Nakai, S. robusta for. glabra Nakai, S. robusta for. subhirsuta Nakai were united with S. wolfii. Morphological variation among different taxa of Syringa (S. patula Nakai, S. micrantha Nakai, S. palibiniana (Nakai) Nakai, S. palibiniana var. longifolia Nakai, S. palibiniana var. kamibayashii (Nakai) Nakai, S. palibiniana var. lactea (Nakai) Nakai, S. venosa Nakai, S. venosa var. lactea Nakai) was continous for most reproductive characters and should be united into S. patula (Palibin) Nakai. Also, the entities of S. amurensis Rupr., S. japonica Maxim., S. amurensis for. bracteata Nakai, S. amurensis var. koreana Nakai, S. amurensis for. longifolia Nakai maintained a certain degree of morphological integrity such as trichome density of leaf beneath, length and wart density of fruit, shape of leaf, and size of bract. A plausible suggestion was that the entities of this group must be united and recognized under one taxon, S. reticulata. The morphological differentiation between S. dilatata and S. oblata was not considered sufficient to warrant recognition of specific status and S. dilatata Nakai were ascertained to S. oblata var, dilatata (Nakai) Rehder. Variation in S. fauriei Lev. is sufficiently discontinuous in lanceolate of leaf shape, main vein like gully and undivided lateral veins, and small fruit to meet the species criterion of consistency, compared with S. riticulata. Results from this current study of Syringa in Korea showed that S. fauriei and S. oblata var. dilatata were Korean endermic plants. while and S. reticulata were treated as northern elements, originated from northeastern China and/or Amur and Ussuri area of Russia.