The order Pyrenulales is a group of mostly lichen-forming fungi within the class Eurotiomycetes. Members of this order are predominantly corticolous, meaning they grow on bark, and are often found in tropical and subtropical regions. They form symbiotic associations with green algae or cyanobacteria, resulting in crustose lichens with a thin, often inconspicuous thallus. Pyrenulales are characterized by perithecioid ascomata, which are flask-shaped fruiting bodies embedded in the substrate, and they produce unitunicate asci with simple, hyaline spores. While most are lichens, some species are lichenicolous or weakly parasitic on other lichens. Their ecological role includes contributing to nutrient cycling and serving as indicators of forest health.