Materials and methods: field observations, microscope technique. Nomenclature: Index Fungorum www.indexfungorum.org. Results: This contribution presents new data on the lichen-forming and lichenicolous fungi of Ukraine. It includes new records and confirmations for 61 species of lichen-forming and 9 species of lichenicolous fungi within Odesa and Volyn regions. The lichens were primarily found at the bases of old oak and pine trees, the circumferences of which is also provided for each locality. The reported taxa belong to the genera Acrocordia, Agonimia, Anisomeridium, Arthonia, Bacidia, Bacidina, Bactrospora, Candelariella, Catillaria, Chaenotheca, Cladonia, Cladophialophora, Coppinsiella, Cornutispora, Didymocyrtis, Diploschistes, Fellhanera, Flavoplaca, Eopyrenula, Halecania, Hypocenomyce, Gyalecta, Gyalectiphila, Kuettlingeria, Lecania, Lecidea, Lecidella, Lepraria, Lichenoconium, Micarea, Mycocalicium, Myrionora, Oxneria, Parmeliopsis, Psoroglaena, Ramalina, Rinodina, Phaeophyscia, Physciella, Physconia, Placynthiella, Polycauliona, Punctelia, Staurothele, Strangospora, Swinscowia, Taeniolella, Thelenella, Trapeliopsis, Trichoconis, Unguiculariopsis, and Verrucaria. Among these, 31 species are reported for the first time for the Volyn region, and 39 species are new to the Odesa region. Notably, Agonimia repleta, Bacidina neosquamulosa, Fellhanera gyrophorica, Gyalecta arbuti, Halecania viridescens, and Swinscowia affinis represent the first records for the lowland part of Ukraine. The species Fellhanera gyrophorica, Gyalecta arbuti, Strigula affinis, and Unguiculariopsis thallophila represent the second records for Ukraine. The study provides recent data from 14 Nature Reserves of national and local significance, including the Danycheve Botanical Reserve, Dibrova Mohylevska Landscape Reserve, Savranskyi Lis Landscape Reserve, Sliusarivskyi Dub Natural Monument, and the Staromanzyrskyi and Tarutynskyi Step Landscape Reserves in the Odesa region, as we as the “Duby zvychaini-veletni” Botanical Natural Monument, Litynskyi Landscape Reserve, Ozerianskyi Zoological Reserve, Radovychivskyi Landscape Reserve, Sosnyna-2 Botanical Natural Monument, Voloshky Landscape Reserve, and Zadybskyi Landscape Reserve in the Volyn region. Keywords: biodiversity, forests, old trees, oak, pine, lowland, Odesa region, Volyn region, Agonimia, Bacidina, Fellhanera, Halecania, Swinscowia, Unguiculariopsis.