Twenty species of lichenicolous fungi are reported on Thamnolia species and discussed. Epithamnolia karatyginii gen. et sp. nov., Capronia thamnoliae sp. nov., Cercidospora epithamnolia sp. nov., C. thamnogalloides sp. nov., C. thamnoliae sp. nov., and Sphaerellothecium thamnoliae sp. nov. (var. thamnoliae, var. taimyricum) are described from Thamnolia. Dacampia thamnoliicola and Phoma thamnoliae are introduced ad interim. Cercidospora lecidomae is reduced to synonymy with C. punctillata. Polycoccum vermicularium is new to Asia, Odontotrema santessonii and O. thamnoliae are new to North America, Cladosporium licheniphilum is new to the Arctic, Thamnogalla crombiei is new toGreenland and Svalbard, Stigmidium frigidum is new to Mongolia and confirmed in the USA, Lichenopeltella thamnoliae is new to Bolivia. Cladosporium licheniphilum and Phaeospora arctica are newly documented on Thamnolia and Lichenopeltella thamnoliae on Thamnolia papelillo var. subsolida. Thamnolia vermicularis, supporting 23 species of lichenicolous fungi, is shown to be the 15th most hospitable lichen species in the world. A worldwide key to 23 species of fungi known to occur on Thamnolia is provided. lichen, new records, new taxa, thamnoliicolous fungi