Muriphaeosphaeria galatellae was collected from Galatella villosa in Russia and is introduced as a novel monotypic genus and species in the family Phaeosphaeriaceae (Pleosporales). Muriphaeosphaeria is distinct from other genera of the family Phaeosphaeriaceae by its unique suite of characters such as, superficial ascomata with an ascomatal wall comprising thin-walled brown cells, cellular pseudoparaphyses, muriform ascospores; and conidiomata with a thick hyaline inner wall layer producing cylindrical to subclavate, 1−3-transversely septate, brown conidia. The asexual morph of M. galatellae developed in cultures when grown on sterilized pine needles and bamboo pieces. A phylogenetic analysis based on combined LSU, SSU and ITS sequence data showed that M. galatellae forms a distinct lineage in Phaeosphaeriaceae. The new genus and species are introduced and compared with other taxa in the family.