The ascomycete genus Gymnoascus is expanded, comprising all Gymnoascaceae with lenticular or discoid (not bivalvate), pigmented ascospores and with ascomata without long, circinate, arcuate, or comb-like appendages. Several species hitherto classified in separate genera are transferred to Gymnoascus. Gymnoascus udagawae spec. nov. is described. A key to the 14 accepted species is given. Gymnoascus durus Zukal is transferred to Ascocalvatia. A checklist of all fungi described in Gymnoascus is given.