This publication presents list of all lichen-forming and lichenicolous fungi known in Iceland. The checklists originates from the lifelong research and extensive collections of Hörður Kristinsson (1937–2023), and has been continuously revised at the Natural Science Institute of Iceland. It currently comprises 838 species of lichens-forming fungi and 144 species of lichenicolous fungi. The list also includes two species regarded as human introduced and two additional fungi that, although neither lichen-forming nor lichenicolous, are regularly encountered by lichenologists because of their habitat preferences. In addition, there are also 10 different varieties listed and five subspecies.