AbstractHeteroacanthella ellipsospora is described as new to science. It is the only known lichenicolous Heteroacanthella, always found parasitizing apothecia and the surrounding thallus of the crustose epiphytic lichen Lecanora carpinea. The new parasite has so far only been found in two Spanish provinces, Jaén and Madrid. The shape and size of its basidiospores, the basidia with acanthoid ornamentation, acanthohyphidia, as well as its parasitic lichenicolous habitat, with a replacement of host tissues by the parasite hymenium, are useful diagnostic characters.