The duckweed species, Landoltia punctata (G. Meyer) D. H. Les & D. J. Crawford (family, Araceae; subfamily,Lemnoideae; common name, dotted duckmeat) was found in artificial wetlands in Jeju SpecialSelf-Governing Province, Republic of Korea; however, it has no formal record in Korea. We identified thisspecies based on morphological characteristics and DNA sequences. We also checked Lemnoideaespecimens in the Korean and Japanese herbaria but found no specimens of La. punctata collected in Koreapreviously. The chloroplast DNA sequence (atpF-atpH) of the species collected from Jejudo was identicalto the other La. punctata sequences in the DNA Data Bank of Japan (DDBJ)/The European MolecularBiology Laboratory (EMBL)/GenBank. Their habitat environments and our herbarium research suggestthat this species has recently become distributed in Korea. This study also provides a key to closelyrelated taxa in the subfamily Lemnoideae, with descriptions of these species.