Two new Orchidantha species discovered in Sarawak, O. micrantha and O. megalantha, are described and illustrated. They may well represent the species with the smallest and the largest flowers currently known in the genus and certainly from Borneo. With its small flowers, O. micrantha is similar to O. borneensis to which it is compared. The large-flowered O. megalantha is compared to the morphologically closest species, O. holttumii, from nearby Brunei. The conservation status of both new species is assessed and a key is provided to all Bornean species.