A new species of Diatrype (Diatrypaceae, Xylariales), D. genheensis, is proposed based on a combination of morphological features and molecular evidence. Diatrype genheensis, from a fallen angiosperm branch in Inner Mongolia, is characterized by having 3–14 perithecia embedded within a stroma, polysporous asci and ascospores that are allantoid, slightly curved, aseptate and subhyaline. The phylogeny of Diatrypaceae was inferred from a combined dataset of ITS and β-tubulin sequences. The phylogenetic tree indicated that D. genheensis belongs to a clade with two other polysporous species, D. betulaceicola and D. larissae. In the phylogenetic trees, D. genheensis was clearly separated from other sampled species of Diatrype. [ABSTRACT FROM AUTHOR]