Eurotiomycetes is a large class of ascomycetes with cleistothecial ascocarps within the subphylum Pezizomycotina,[1] currently containing around 3810 species according to the Catalogue of Life.

[4] The class Eurotiomycetes was circumscribed in 1997 by Swedish mycologists Ove Erik Eriksson and Katarina Winka.

In 2001, the second subclass, Chaetothyriomycetidae, was erected to accommodate Chaetothyriales and its sister group Verrucariales, as well as Pyrenulales since 2004.

[4] The remaining subclasses were created through more phylogenetic analyses to accommodate outlying taxa or newly discovered groups: Mycocaliciomycetidae in 2007,[5] Coryneliomycetidae[6] and Sclerococcomycetidae in 2016,[7] and lastly Cryptocaliciomycetidae in 2021.

[8] The following cladogram shows the relationships between all Eurotiomycetes orders and monotypic subclasses as of 2021:[7][8] Chaetothyriales Verrucariales Phaeomoniellales Pyrrenulales Onygenales Arachnomycetales Eurotiales Cryptocaliciomycetidae Coryneliomycetidae Sclerococcomycetidae Mycocaliciomycetidae Lecanoromycetes The class Eurotiomycetes forms a clade with Lecanoromycetes, the largest lichenized class of fungi.