Rhodamnia kamialiensis and Xanthomyrtus splendens are described from ultrabasic substrates in the Kamiali Wildlife Management Area, Papua New Guinea. The new species are known only from their type gatherings and are preliminarily assigned the IUCN status of “critically endangered.” Rhodamnia kamialiensis has much larger leaves and more abruptly prolonged leaf apices than other species in its genus. The glossy upper leaf surface with flat or impressed midrib separates Xanthomyrtus splendens from its congeners.