The revealed lichen diversity of the historical territory Osinovaya Roscha has a total of 230 species, including 206 lichenized, 17 lichenicolous, and seven non-lichenized saprobic fungi. Epithamnolia xanthoriae is new to North-Western European Russia; Arthonia vinosa, Caloplaca ahtii, Cladonia merochlorophaea, Hawksworthiana peltigericola, Lecania erysibe, Rinodina pityrea, Rosel-liniella cladoniae, Taeniolina scripta, and Trichonectria rubefaciens are new to St. Petersburg. In total, eight lichen species reported from Osinovaya Roscha are red-listed in St. Petersburg. In spite of small size of this area, the lichen diversity of Osinovaya Roscha is high compared to other territories in the city, and is worthy of protection.