Aspergillus, genus of fungi in the order Eurotiales (phylum Ascomycota, kingdom Fungi) that exists as asexual forms (or anamorphs) and is pathogenic (disease-causing) in humans. Aspergillus niger causes black mold of foodstuffs; A. flavus, A. niger, and A. fumigatus cause aspergillosis in humans. A. oryzae is used to ferment sake, and A. wentii to process soybeans. Three other genera have Aspergillus-type conidia (asexually produced spores): Emericella, Eurotium, and Sartorya.