The Pleosporales is the largest order in the fungal class Dothideomycetes. By a 2008 estimate, it contained 23 families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying plant material in fresh water, marine, or terrestrial environments, but several species are also associated with living plants as parasites, epiphytes or endophytes. The best studied species cause plant diseases on important agricultural crops e.g. Cochliobolus heterostrophus, causing southern corn leaf blight on maize, Phaeosphaeria nodorum causing glume blotch on wheat and Leptosphaeria maculans causing a stem canker on cabbage crops (Brassica). Some species of Pleosporales occur on animal dung, and a small number occur as lichens and rock-inhabiting fungi.

Dothideomycetes is the largest and most diverse class of ascomycete fungi. It comprises 11 orders 90 families, 1,300 genera and over 19,000 known species. Wijayawardene et al. in 2020 added more orders to the class.