Castanopsis hypophoenicea is a tree in the family Fagaceae. The specific epithet hypophoenicea means 'crimson beneath', referring to the indumentum on the leaf underside.
Castanopsis hypophoenicea grows as a tree up to tall with a trunk diameter of up to . The greyish bark is rough, sometimes smooth. The coriaceous leaves measure up to long. Its ovoid or ellipsoid nuts measure up to long.
Castanopsis hypophoenicea is endemic to Borneo. Its habitat is dipterocarp forests up to elevation.