Illyria, the name anciently given to a broad stretch of mountainous country of varying extent lying E. of the Adriatic Sea. The Illyrians were the last Balkan people to be civilised; becoming a Roman province 35 B.C., Illyria furnished several emperors, among them the notorious Diocletian. Constantine extended the province to include all the country S. of the Danube; at the division of the empire, Greece and Macedonia went to the East, the rest to the West; the name was revived by Napoleon, but has since been dropped.