Arthoniomycetes are a class of ascomycete fungi.

[2] Most of the taxa in these orders are tropical and subtropical lichens.

Phylogenetic analysis supports the monophyly of this class.

[4] Taxa have apothecia, cup- or saucer- shaped ascoma in which the hymenium is exposed at maturity.

These apothecia are bitunicate - with clearly differentiated inner and outer walls.