A taxonomic study of the genus Agathidium (Coleoptera: Leiodidae) from Korea, Part I. -A taxonomic study of the genus Agathidium from Korea is presented. Nine species including five new species {Agathidium mwyeongi sp. n., A. bockshini sp. n., A. leesunshini sp. n., A. odaesanense sp. n., and A. choi sp. n.) are recognized, two of which are reported as new to Korea {Agathidium cribratum Poitevin and A. multitodum Hoshina). A key for the Korean species of the two subgenera, Cyphoceble and Neoceble, of the genus Agathidium and illustrations of diagnostic features are provided.