The Krkonoše Mountains (Giant Mountains), straddling the border between the Czech Republic and Poland, represent a unique natural region in Central Europe, featuring Mount Sněžka (1,603 m), the highest peak in the Czech Republic. This area is protected by two national parks and is particularly notable for its rare arctic-alpine tundra habitat, covering approximately 47 square kilometers, which is crucial for biodiversity conservation and harbors numerous glacial relict and endemic species. This study initiated a new survey of the local lichen biota in the Czech part of the Krkonoše Mountains through excursions conducted between 2011 and 2024. Our research prioritized the highest peaks to capture high-mountain species threatened by climate change. We report here 270 lichen taxa and 3 lichenicolous/non-lichenized fungi from 43 localities. Four species are new to the Czech Republic: Lepraria celata, Miriquidica invadens, M. subplumbea, and Rimularia gyrizans. Three species are potentially new to science: Bacidina aff. assulata, Porpidia aff. islandica and Rhizocarpon aff. lavatum. Lecidella patavina, Porpidia pachythallina, and Toniniopsis dissimilis are reported from their second localities in the Czech Republic. Ochrolechia frigida and Porina mammillosa were collected on unusual substrates – as epiphytes. We hypothesize that Lecanora latro and L. leptacina represent ecological forms of a single species. Other remarkable records are represented by Alectoria nigricans, Allantoparmelia alpicola, Arctoparmelia incurva, Bellemerea diamarta, Cladonia crispata, Fuscidea austera, Helocarpon crassipes, Lecanora latro, Lecidea auriculata, Micarea marginata, Miriquidica garovaglii, M. pycnocarpa, Protoparmelia memnonia, P. phaeonesos, Psorinia conglomerata, Umbilicaria crustulosa, U. nylanderiana, and U. proboscidea. Key words: arctic-alpine lichens, arctic-alpine tundra, biodiversity, saxicolous lichens.