Lecanoromycetes is a large and diverse class of fungi within the phylum Ascomycota, primarily known for forming lichens, symbiotic associations between fungi and photosynthetic partners such as algae or cyanobacteria. Members of this class are mostly sac fungi, producing sexual spores in specialized structures called asci, often contained in fruiting bodies known as apothecia. They exhibit a wide range of morphologies, from crust-like to leaf-like thalli, and are ecologically important as pioneers in colonizing harsh environments, contributing to soil formation, nutrient cycling, and serving as indicators of air quality. Lecanoromycetes includes many species adapted to terrestrial habitats but can also be found on rocks, trees, and soil, highlighting their adaptability and ecological significance.