We report 152 species of lichenized and lichenicolous fungi from the central Aegean island of Astipalea, Greece, based on morphological, anatomical, chemical and macromolecular examination. Amandinea oleicola, Arthonia sanguinea and Endocarpon latzelianum are reported for the first time from Greece. Glaucomaria sulphurata and Lepra parotica are introduced as new combinations. Ramalina aegaea is described as a species new to science because its ITS sequences deviate from the morphologically similar R. requienii and agree with those of R. canariensis. A genetically distinct population of Calogaya arnoldii present in the Aegean is left unnamed because it shows no differentiating morphological characters. The ITS sequences of Xanthoria monofoliosa show that this species is widespread in the Aegean, and the sequences available in GenBank suggest that its range includes the Mediterranean climate zones of both the northern and southern hemispheres. Keywords: Aegean, Astipalea, cryptic species, fungal diversity, Greece, lichens, ITS, new species, population genetics.