Tolypocladium

Tolypocladium is a genus of filamentous fungi in the phylum Ascomycota. Members of the genus are found in soil and decaying organic matter, and several species act as parasites of other fungi or insects, while others live as saprobes or endophytes. They produce hyphae with conidiophores that bear conidia, and many species form both asexual and, when present, sexual morphs under appropriate conditions.

Tolypocladium inflatum is the best-known species and has gained prominence for producing cyclosporine A, a cyclic peptide immunosuppressant used to prevent organ transplant rejection. The discovery of cyclosporine A from T. inflatum in the 20th century highlighted the genus's potential for secondary metabolite production. Other Tolypocladium species have been studied for additional bioactive compounds and for their ecological roles as mycoparasites or occasional pathogens of insects or other fungi.

Taxonomy and phylogeny have been revised with molecular data, and Tolypocladium is placed within the larger order Hypocreales of the class Sordariomycetes, though generic boundaries in this group have changed as new data emerge. The genus comprises multiple species described from diverse environments, with morphology typically featuring filamentous hyphae and conidiophores producing asexual spores; many species also produce sexual structures in natural conditions or under laboratory culture.