A new genus and species of gnathiid isopod, Tenerognathia visus, is described on the basis of three male specimens sampled from coral rubble infauna in the Ryukyus, Japan. The dorsal view of the gnathiid, having small mandibles, large eyes, and a slender body, is more similar to larvae than adult males of other gnathiid species. The pylopod of Tenerognathia resembles that of Caecognathia, Elaphognathia, and Gnathia in the number of articles, but is distinctly more elongated. Morphologies of the mandibles, cephalon, and thorax are compared with these three genera.