Pannonia (pănō´nēə), ancient Roman province, central Europe, southwest of the Danube, including parts of modern Austria, Hungary, Slovenia, Croatia, and Serbia. Its natives, the warlike Pannonians, were Illyrians. Their final subjugation by Rome took place in AD 9. Pannonia was divided c.AD 103 into the provinces of Upper Pannonia and Lower Pannonia. Important centers were Carnuntum (near Hainburg, Austria), Vindobona (Vienna), Aquincum (Budapest), and Sirmium. Pannonia was abandoned by the Romans after 395.