Version 25 of the checklist of lichen-forming, lichenicolous and allied fungi occurring in North America north of Mexico is presented. It includes a total of 6,097 species in 871 genera, with an additional 64 subspecies, 88 varieties, and 8 forms. The total number includes 780 lichenicolous fungi, 135 saprophytic fungi related to lichens or to lichenicolous fungi, and 117 taxa of varying and/or uncertain biological status. In all, 174 families in 73 orders of fungi are represented. The majority of these belong to Ascomycota, but 9 families in 9 orders of Basidiomycota are included. A supra-generic classification is included as an Appendix. Keywords. – Canada, floristics, lichens, nomenclature, United States.