Chaetomium atrobrunneum is a darkly pigmented mould affiliated with the fungal division, Ascomycota. This species is predominantly saprotrophic, although it has been known to infect animals including humans, showing a proclivity for the tissues of the central nervous system. Chaetomium atrobrunneum was described in 1949 from a mouldy military mattress cover obtained from the island of Guadalcanal.