Fungi and lichens of the Brissago Islands (Switzerland). This contribution summarizes current knowledge of the mycological flora of the Brissago Islands, covering both fungi and lichens. For each group, scientific studies and observations are reviewed. For fungi, special focus is given to the macrofungi inventory conducted by the Locarno Mycological Society in the 1980s and 1990s. The collected data were reanalyzed, visualized, and summarized for the first time. Approximately 15% of the species assessed on the Red List are at risk of extinction. Land use, cultivation practices, vegetation composition, and cultivated species influence fungal communities, with significant impacts on ecological processes and interactions. Certain introduced fungi, brought in with ornamental plants, can severely damage the arboretum. For lichens, limited observations exist; a 2023 inventory will help address this gap. Preliminary findings indicate the Islands host the largest cantonal population of the highly endangered epiphytic lichen Collema subflaccidum (on Populus nigra subsp. nigra trunks), for which the Canton holds special conservation responsibility. In general, preserving the diversity of (micro-)habitats in the riparian zone, including wet and dry rock outcrops, native floodplain trees, dead wood, and driftwood, is essential for maintaining fungal biodiversity. Keywords: Ambrosiella, botanical garden, Collema subflaccidum, conservation, lichenised fungi, neomycetes, urban biodiversity.