Coleroa chaetomium is a phytopathogenic ascomycete fungus in the family Phacidiaceae (order Rhytismatales), recognized as a cause of leaf spot diseases on various herbaceous plants and grasses. Members of the genus Coleroa produce characteristic black, setose (bristle-bearing) apothecia on infected plant tissue, serving as the primary identification feature. The fungus overwinters in dead plant material, releasing ascospores in spring to infect new growth. While typically regarded as a minor pathogen or saprophyte on senescent tissue, it can occasionally cause significant spotting and premature leaf drop under favorable conditions of high moisture and moderate temperatures. Coleroa chaetomium has been recorded from a range of host plants across temperate regions of Europe and North America, with some records extending to other continents. Its taxonomy has been subject to revision as molecular techniques clarify relationships within the Rhytismatales. The ecological role of Coleroa species includes contributing to the decomposition of plant litter and nutrient cycling in terrestrial ecosystems, functioning at the interface between parasitism and saprotrophism. More detailed ecological studies of this fungus remain limited compared to economically significant pathogens.