Coelostegia is a small Bombacaceae genus from western Malesia (Peninsular Malaysia, Sumatra and Borneo). Soegeng Reksodihardjo (1960), in his revision of the genus recognizes five species. Since Soegeng's work no attempt at a revision has been made and no new species have been described. Coelostegia and Durio are very difficult to distinguish by vegetative characters only. Flower and fruit characters are very important for species recognition. During field work in the Kayan Mentarang National Park, East Kalimantan, Indonesia, the author collected specimens of a Coelostegia-like plant that proved to be a new species. This species is described below.