Buxus microphylla (Japanese Box or Littleleaf Box) is a species of Buxus native to Japan and Taiwan.
It is an evergreen shrub or small tree growing to 2–3 m tall. The leaves are bright green, 10–25 mm long, oval with a rounded or notched tip.
The species was first described from cultivated plants of in Japan of unknown origin; these are dwarf shrubs only growing to 1 m tall, with small leaves less than 18 mm long. Wild box plants in Japan differ somewhat, growing to 2–3 m tall with leaves up to 25 mm long; they are sometimes distinguished as Buxus microphylla var. japonica (Muell.-Arg.) Rehder & Wilson (syn. B. japonica Muell.-Arg.).
Plants from Taiwan are distinguished as Buxus microphylla var. tarokoensis S.Y.Lu & Y.P.Yang.
Plants from China and Korea formerly often cited as Buxus microphylla var. sinica are now treated as a distinct species Buxus sinica.
The species is grown as an ornamental plant both in its native area and elsewhere in temperate regions of the world.
Buxus microphylla var. compacta and similar cultivars are commonly used for bonsai.