O. japonica may refer to: Obesotoma japonica, a sea snail species Olivella japonica, a sea snail species Orixa japonica, a shrub of Japan and Korea Osmunda japonica, the Japanese royal fern or Japanese flowering fern, a fern species native to eastern Asia, including Japan, China, Korea, Taiwan and the far east of Russia on Sakhalin Ostrya japonica, the Japanese hop-hornbeam, a tree species native to Japan, Korea and China See also Japonica (disambiguation)