The phytophagous eurytomid wasp Eurytoma bryophylli sp. n. from Madagascar is described and illustrated with scanning electron micrographs. Its host plant, Bryophyllum delagoense (Ecklon & Zeyher) Schinz, is indigenous to Madagascar but has been introduced to other countries as an ornamental, becoming invasive in some places, including Queensland, Australia. This new Eurytoma species tunnels in the leaves and tests showed it to be a suitable candidate for the biocontrol of this weed. The generic and specific identities of the new species are discussed and its distinguishing characters are defined. The new species is assigned to Eurytoma Illiger on the basis of structures on the back of the head. It belongs to an assemblage of Eurytoma species, some of which are known phytophages. It shows resemblance to species of Bruchophagus Ashmead and Systole Walker, but critical differences are pointed out.