This paper gives a comprehensive list of the species of Nudibranchia from Japanese waters. The following eleven are recognized as new species: Euphurus ornatus, Polycera fujitai, Goniodoris glabra, Okenia barnardi, Noumea nivalis, Geitodoris lutea, Thordisa amakusana, Discodoris pallida, Cuthona emurai, C. ornata, Favorinus pacificus. The following two are regarded as new subspecies : Marionia pustulosa odhneri, Baeolidia major amakusana. Two new specific names have been proposed for the previously noted forms :-Phyllidia japonica, Cuthona japonica.