A new species of Ixora is described from New Caledonia, the third strictly cauliflorous species known there, and the fourth in the whole genus (c. 500 species). The main diagnostic character is the strongly ribbed fruit, never observed in New Caledonian Ixora, nor, probably, in other representatives of the genus. Ixora aoupinieensis Hoang & Mouly seems endemic to the north-eastern mountains of the main island, and grows along highly elevated creeks. This species, a very localized non-obligatory rheophyte, is very threatened, because of extensive forest exploitation. The IUCN status of Ixora aoupinieensis is Endangered (EN) species, meaning it necessitates a careful protection.