Castanopsis borneensis is a species of tree in the family Fagaceae. The specific epithet ' is from the Latin, meaning 'of Borneo'.
Castanopsis borneensis grows as a tree up to tall with a trunk diameter of up to . The bark is smooth or fissured. The coriaceous leaves measure up to long. Its ovoid nuts measure up to long.
Castanopsis borneensis is endemic to Borneo. Its habitat is lowland dipterocarp and kerangas forests, to altitude.