Epirus (/ɪˈpaɪrəs/) is a geographical and historical region in southeastern Europe, now shared between Greece and Albania. Classical Epirus roughly lay between the Pindus Mountains in the east and the Ionian Sea in the west, and between the Acroceraunian Mountains in the north and the Ambracian Gulf in the south. It is currently divided between the region of Epirus in northwestern Greece and the counties of Gjirokastër and Vlorë in southern Albania. The largest city and seat of the Greek administrative region of Epirus is Ioannina.
A rugged and mountainous region, in classical antiquity Epirus was the north-west area of ancient Greece. It was inhabited by the Greek tribes of the Chaonians, Molossians, and Thesprotians. It was home to the sanctuary of Dodona, the oldest oracle in ancient Greece, and the second most prestigious after Delphi. Unified into a single state in 370 BC by the Aeacidae dynasty, Epirus achieved fame during the reign of Pyrrhus of Epirus who fought the Roman Republic in a series of campaigns. Epirus subsequently became part of the Roman Republic along with the rest of Greece in 146 BC, which was followed by the Roman Empire and Eastern Roman Empire.