An inventory of the lichens of Bruce Peninsula National Park and Fathom Five National Marine Park in the Georgian Bay area of southern Ontario was carried out by 30 lichenologists participating in the 2008 Tuckerman Workshop. A list of 370 species of lichens, related fungi and lichenicolous fungi was compiled, documenting that the parks are remarkably rich in lichens, including many rarities. Following the park inventory, an additional 21 lichens from Bruce County are listed based on the published literature and other recent collections. Twelve lichens, one related fungus and nine lichenicolous fungi are additions to the Canadian lichen flora: Acarospora moenium, Bagliettoa baldensis, Biatora ocelliformis, Caloplaca flavocitrina, Clavascidium umbrinum, Dermatocarpon dolomiticum, D. muhlenbergii, Heppia adglutinata, Lecania cuprea, Opegrapha mougeotii, Thelidium minutulum, Heteroplacidium compactum; Mycoglaena myricae; Capronia peltigerae, Lichenoconium erodens, Muellerella hospitans, M. ventosicola, Phaeopyxis punctum, Phoma cladoniicola, Plectocarpon cladoniae, Polycoccum minutulum, Tremella candelariellae. An additional 35 lichens, two related fungi, and 13 lichenicolous fungi are new for Ontario: Acarospora macrospora, Biatora chrysantha, B. turgidula, Biatorella hemisphaerica, Botryolepraria lesdainii, Buellia griseovirens, Caloplaca saxicola, C. subsoluta, Cladonia atlantica, Clauzadea monticola, Cliostomum leprosum, Diplotomma venustum, Enterographa zonata, Farnoldia hypocrita, Gyalecta foveolaris, Hymenelia heteromorpha, Lempholemma isidiodes, Lepraria caesiella, L. eburnea, Leptogium intermedium, Opegrapha rufescens, Placidium squamulosum, Porpidia contraponenda, P. macrocarpa f. nigrocruenta, P. soredizodes, P. superba, Pseudosagedia aenea, Psorotichia schaereri, Pycnora sorophora, Sagiolechia protuberans, Thelocarpon epibolum var. epithallinum, Trapeliopsis pseudogranulosa, Vezdaea acicularis, Violella fucata and Xylographa vitiligo; Epigloea pleiospora and Sarea difformis; Clypeococcum hypocenomycis, Cornutispora ciliaris, Lettauia cladoniicola, Lichenodiplis lecanorae, Marchandiomyces corallinus, Muellerella erratica, M. lichenicola, Nectriopsis parmeliae, Phoma cladoniicola, Pronectria robergei, Refractohilum peltigerae and Spirographa fusisporella. A total of 77 range extensions are presented, many of which are significant discoveries, but others of which represent the first Canadian records of species that have been found to be common and widespread in adjacent regions of the United States. With regard to lichens, the parks now constitute the best-studied area of their size in Ontario. Eiglera flavida is an additional report for Bruce County not collected on the workshop; it is also new for Ontario. Of the habitats visited in the park, the shoreline cliffs and adjoining forests at Halfway Log Dump are the most rich in species (223). Flowerpot Island was almost as diverse (196). Although somewhat less diverse, the alvars (with 149 species) also contained several remarkable records and a surprising number of species.