Fagus crenata, known as the Japanese beech, Siebold's beech, or buna, is a deciduous tree of the beech genus, Fagus, of the family Fagaceae. It is native to Japan where it is widespread and often one of the dominant trees of Japan's deciduous forests. It is found from the Oshima Peninsula in Hokkaidō south to the Ōsumi Peninsula in Kyūshū. In north-east Honshū it grows in large stands from sea level up to 1400 metres but in the south-west of its range it is restricted to mountainous areas and occurs in small, isolated populations. It grows in well-drained, loamy or sandy soils.
It reaches 35 metres in height. The crown is rounded and the bark is smooth and grey. The simple leaves are arranged alternately along the branch. They are broadest towards the base and have 7 to 11 pairs of veins. The nut has a short thick stalk, 15 mm long. There are flattened green whiskers at the base of the husk of the nut. The flowers are wind-pollinated. The young leaves and seeds are edible.