Molybdenite occurs mainly in three mineralization types in Greece: (a) porphyry Mo-Cu-(±Te-Ag-Au), (b) reduced intrusion-related Mo-W systems (skarn, intrusion-hosted) and (c) shear zone-related Cu-Au-Bi-Mo. In porphyry-Mo-Cu prospects the molybdenite is the main ore constituent together with pyrite in quartz stockworks crosscutting sericite±carbonate altered porphyry stocks (dacite at Pagoni Rachi/Kirki, Myli/Esymi, Konos/Sapes, Melitena/Rhodopi and Stypsi/Lesvos; microgranite at Ktismata/Maronia; monzonite at Sardes/Limnos, Fakos/Limnos and Skouries/Chalkidiki). Reduced intrusion-related systems are characterized by the presence of molybdenite, pyrite and wolframite-scheelite in intrusion-hosted sheeted quartz veins and/or dissemination (granodiorite at Kimmeria/Xanthi, Plaka/Lavrion and leucogranite at Pigi/Kilkis and Seriphos) and skarn-hosted ores (Kimmeria/Xanthi). Finally in the shear-zone Stanos prospect molybdenite accompanies chalcopyrite, native Bi, Bi-tellurides and sulfosalts. The studied molybdenites display a wide spectrum of their rhenium content ranging from almost Re-free molybdenites at Stanos, to very low-Re molybdenite in the intrusion-related systems (Lavrion, Serifos, Pigia and Kimmeria), and high to ultrahigh-Re molybdenites in the northern Greek porphyries. The rare mineral rheniite (ReS2), occurs along with Fe-Cu sulfides, Pb oxides, and native Sn in Pagoni Rachi and Konos prospects. Rheniite and high-Re molybdenite precipitated under oxidizing conditions and from relatively acid hydrothermal solutions, whereas Re-poor molybdenites are indicative of reduced conditions mostly dominant in the intrusion-related systems. At the northern Greek porphyry-Mo prospects, magmas previously enriched from their mantle source rocks were responsible for extreme contents of rhenium in molybdenite.