Hypomyces is an important genus of fungicolous fungi associated with different ascomycetes and basidiomycetes. Numerous researchers have conducted morphological and molecular studies on this genus. In this study, we collected submerged branches of Fagus sp. from Mazandaran Province in Iran, from which a fungal isolate was obtained. Morphology coupled with maximum likelihood and Bayesian inference analyses of the combined ITS, LSU, and rpb2 sequence data showed it is a novel taxon (Hypomyces iranica). The morphology of the newly described species is compared with its sister taxa, and a comprehensive description and micrographs are provided.