Obsidians from Grotta dell'Uzzo and Monte Cofano (Trapani, western Sicily) represent the first studied finding of obsidian in Sicily. The samples from Grotta dell'Uzzo originate on the excavation of three trenches, those from Monte Cofano are surface artifacts from the area on which the Greek town of Heraclea was established. Comparative XRF elemental analysis leads us to the conclusion the 61per thousand of the obsidian artifacts from Grotta dell'Uzzo originate on Lipari and 39per thousand, of peralkaline sodic composition, come from Pantelleria. The Liparian artifacts are very close to obsidian from the Papezca beach. The Pantellerian artifacts belong to the Balate dei Turchi, while 4 samples originate on the Gelkhamar dome. Finally, the obsidians from Monte Cofano originate both on Lipari and Pantellaria; only one artifact remains of unidentified provenance.