The Illyrians, ethnically akin to the Thracians, had originally inhabited a large area from the Istrian Peninsula to northern Greece and as far inland as the Morava River, but Celtic invasions during the fourth century BCE push the Illyrians southward from the northern Adriatic coast, and hereafter their territory does not extend much farther north than the Drin River.

Illyrian society, like that of the Thracians, is organized around tribal groups who often fight wars with one another and with outsiders.