Buglossoporus quercinus is widely distributed across Europe, within the range of Quercus robur. Throughout the area, in which it appears, it is rare or very rare. B. quercinus is associated with large old oaks (Quercus, usually Q. robur), whose numbers are decreasing due to ongoing changes in the environment. It was added to the Red Lists of fungi in a number of countries, along with awaiting inclusion in the IUCN Red List. In this study we have critically analysed the existing data on the occurrence of B. quercinus in Poland. We have presented two new localities of the species in Poland, as well as new records in the Białowieża National Park, the only place, where this species had been previously recorded in Poland. Selected trees and logs inhabited by B. quercinus were characterized. We have indicated the number of observed basidiomata, their phenology, and the sizes of the largest specimens. We have identified eight fungal species (Bisporella citrina, Daedalea quercina, Hapalopilus croceus, Hymenochaete rubiginosa, Laetiporus sulphureus, Mycena galericulata, M. inclinata, Xylobolus frustulatus) that coexist with B. quercinus. Based on the new distribution data for B. quercinus in Poland, this species should be classified as Endangered (EN) according to the IUCN Red List criteria.

Keywords: wood-decay fungi, rare species, fungi protection, Red List, Central Europe, oak