The monograph presents the results of generalization and critical analysis of data accumulated over the 240-year history of lichen studies on the territory of modern Belarus, including the author's original materials. As a result of the work, 722 species of lichens and lichenicolous fungi are accepted for the territory of the country, of which two species are described by the author as new to science, 78 species are reported for the first time for Belarus. 99 species are excluded from the list of lichen biota. Taxonomical, geographical, biomorphological and ecological-substrate analyzes of the lichen biota of Belarus were carried out for the first time. All the main features and trends in the dynamics of lichen species diversity are identified and characterized. A system of life forms of lichens of forest communities is proposed.