Ascomycota, the most speciose phylum of fungi, is a complex entity, comprising three diverse subphyla: Pezizomycotina, Saccharomycotina, and Taphrinomycotina. The largest and most diverse subphylum, Pezizomycotina, is a rich tapestry of 16 classes and 171 orders. Saccharomycotina, the second largest subphylum, is a diverse collection of seven classes and 12 orders, while Taphrinomycotina, the smallest, is a unique assembly of six classes and six orders. Over the past decade, numerous taxonomic studies have focused on the generic, family, and class classifications of Ascomycota. These efforts, well-documented across various databases, are crucial for a comprehensive understanding of the classification. However, the study of taxonomy at the ordinal level, a crucial tier in the taxonomic hierarchy, has been largely overlooked. In a global collaboration with mycologists and lichenologists, this study presents the first comprehensive information on the orders within Pezizomycotina and Taphrinomycotina. The recent taxonomic classification of Saccharomycotina has led to the exclusion of this subphylum from the present study, as an immediate revision is not necessary. Each order is thoroughly discussed, highlighting its historical significance, current status, key identification characteristics, evolutionary relationships, ecological and economic roles, future recommendations, and updated family-level classification. Teaching diagrams for the life cycles of several orders, viz. Asterinales, Helotiales, Hypocreales, Laboulbeniales, Meliolales, Mycosphaerellales, Ophiostomatales, Pezizales, Pleosporales, Phyllachorales, Rhytismatales, Sordariales, Venturiales, Xylariales (Pezizomycotina) and Pneumocystidales, Schizosaccharomycetales and Taphrinales (Taphrinomycotina) are provided. Each diagram is explained with a representative genus/genera of their sexual and asexual cycles of each order. Within Pezizomycotina, Dothideomycetes contains the highest number of orders, with 57, followed by Sordariomycetes (52 orders), Lecanoromycetes (21 orders), Eurotiomycetes and Leotiomycetes (12 orders each), Laboulbeniomycetes (3 orders), and Arthoniomycetes and Xylonomycetes (2 orders each). Candelariomycetes, Coniocybomycetes, Geoglossomycetes, Lichinomycetes, Orbiliomycetes, Pezizomycetes, Sareomycetes, and Xylobotryomycetes each contain a single order, while Thelocarpales and Vezdaeales are treated as incertae sedis within Pezizomycotina. Notably, the classes Candelariomycetes, Coniocybomycetes, Geoglossomycetes, Sareomycetes, and Xylonomycetes, all recently grouped under Lichinomycetes, are treated as separate classes based on phylogenetic analysis and current literature. Within Lecanoromycetes, the synonymization of Sporastatiales with Rhizocarpales and Sarrameanales with Schaereriales is not supported in the phylogenetic analysis. These orders are retained separately, and the justifications are provided under each section as well as in the discussion. Within Leotiomycetes, the order Medeolariales, which was once considered part of Helotiales, is treated as a distinct order based on phylogenetic evidence. The classification of Medeolariales may change as more data becomes available from different gene regions. Lahmiales (Leotiomycetes) is not included in the phylogenetic analysis due to a lack of molecular data. Sareomycetes and Xylonomycetes are treated as separate classes. Spathulospora mixed with Lulworthiales and the inclusion of Spathulosporales within Lulworthiomycetidae is supported and extant molecular sampling is important to resolve the phylogenetic boundaries of members of this subclass. The majority of the classes of Pezizomycotina and Taphrinomycotina formed monophyletic clades in the phylogenetic analysis conducted based on SSU, LSU, 5.8S, TEF and RPB2 sequence data. However, Arthoniomycetes nested with the basal lineage of Dothideomycetes and formed a monophyletic clade also known as the superclass, Dothideomyceta. In Taphrinomycotina, a single order is accepted within each class.
