O. japonica

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