Boubínský prales virgin forest is the best-preserved montane Picea-Fagus-Abies forest in the Czech Republic. Its core area (46.67 ha), grown with original montane forest never cut nor managed by foresters, has been protected since 1858. It represents the centre of the present-day nature reserve (685.87 ha). A detailed inventory of its fungal diversity was carried out in 2013-2014. Ten segments differing in habitat and naturalness were studied (235 ha). The total number of species was 659, with the centre of diversity in the core area (503 species) followed by the neighbouring segments grown by natural forests minimally influenced by man. When literature and herbarium data are added, the total diversity reaches a total of 792 taxa. The locality represents a unique refugium for some borealmontane fungi (e.g. Amylocystis lapponica, Laurilia sulcata, Pholiota subochracea), a high number of rare species preferring old-growth forests (Antrodia crassa, A. sitchensis, Baeospora myriadophylla, Chrysomphalina chrysophylla, Fomitopsis rosea, Ionomidotis irregularis, Junghuhnia collabens, Skeletocutis odora, S. stellae, Tatraea dumbirensis), wood-inhabiting and mycorrhizal fungi confined to Abies (Panellus violaceofulvus, Phellinus pouzarii, Pseudoplectania melaena, Lactarius albocarneus), and a high number of indicators of well-preserved Fagus forests (e.g. Climacodon septentrionalis, Flammulaster limulatus, Pholiota squarrosoides). Several very rare fungi are present, e.g. Chromosera cyanophylla, Cystoderma subvinaceum and Pseudorhizina sphaerospora. The value of the local mycobiota is further emphasised by the high number of protected and Red List species. Comparison with other Central European old-growth forests has confirmed that Boubínský prales is a mycological hotspot of European importance.