Epirus, or Epeirus, an ancient country north of Greece. The region lies between the Pindus Mountains and the Ionian Sea, and is now divided between northwestern Greece and southern Albania. The most noted king of Epirus was Pyrrhus, who fought the Romans, 281–275 B.C. Epirus was annexed by Rome in 168 B.C. and when the empire was divided in 395 A.D. it became part of the Eastern Roman, or Byzantine, Empire.

When the Fourth Crusade turned against Constantinople and the Byzantine Empire in 1204, Epirus was one of the few imperial regions not conquered. It was made into an independent despotate (kingdom) by Michael Angelus Comnenus, a Byzantine noble. His successor, Theodore, expanded the despotate to the Aegean Sea in 1222 and declared himself Byzantine emperor. Theodore fought his way to the walls of Constantinople, but then turned back to meet a Bulgarian attack.

In the 1240's the Nicaeans, Byzantines of Asia Minor who considered themselves the true imperial heirs, drove back the Bulgarians and took Epirus' eastern lands. In 1259 the despotate was reduced to a vassal state of Nicaea, which in 1261 captured Constantinople and restored the Byzantine Empire. Epirus remained a nominal part of the empire until overrun by Serbs in the mid-14th century. Expansion of the Turks into the Balkans later in the century caused many decades of chaos. In 1461 Epirus was annexed by the Ottoman (Turkish) Empire.