Cleistanthus sumatranus is an accepted name of a tree species in the genus Cleistanthus (family Phyllanthaceae). No subspecies are listed in the Catalogue of Life.
It is found in dense deciduous or evergreen forests, from sea level to approximately 700m (2,300feet) in Brunei, Cambodia, southern China, Indonesia, Malaysia, Philippines, Singapore, Thailand, and Vietnam. In Chinese, it is called 闭花木 bi hua mu and in Vietnamese Cách hoa (Sumatra).
Cleistanthus sumatranus is an evergreen tree, growing up to 18m (59feet) tall.
The leaves have NaNmm petioles with elliptical leaf blades which are typically NaNmm by NaNmm. Flowers are small, each with five sepals and five small petals (both male and female), with up to seven occurring in axillary fascicles, subtended by normal or smaller leaves, or on leafless spike-like axes. Flowering is typically from March–August; fruiting from April–October. The capsules are red and ovoid, approximately 10by, containing seeds which are usually single and up to 6mm in diameter.