Illyria (anc. Illyricum and Illyris; Ger. Illyrieri), a name anciently applied to all the countries on the east coast of the Adriatic, the adjacent islands, and western Macedonia, inhabited by the Illyrians, a tribe believed to have had a common origin with the Thracians. Philip of Macedon subdued the Illyrians east of the river Drilo (now Drin), 359 B. C. Illyricum was subsequently divided into Illyris Graeca and Illyris Barbara. The latter soon became a Roman province, designated as Illyris Romana, and included a part of the modern Croatia, the whole of Dalmatia, almost the whole of Bosnia, and a part of Albania. The principal tribes after whom the districts were called were the Japydes, Liburni, and Dalmatians. The Liburni were the first subdued by the Romans; and after the conquest of the Dalmatians, in the reign of Augustus, the entire country became a Roman province. After that time the Illyrians, and particularly the Dalmatians, formed an important part of the Roman legions, and were esteemed the most warlike of the empire. Illyris Graeca, or Illyria proper, embraced the greater part of the modern Albania. The territory of this division consisted principally of mountain pastures, with some fertile valleys.

The various tribes of the Grecian Illyrians were generally poor, rapacious, and fierce; in earlier times the tribe of the Autariatae held the first rank as warriors. They had the customs of tattooing and of offering human sacrifices, and were always ready to sell their military services to the highest bidder, like the modern Albanian Shkipetars, in whom probably their blood yet flows. The Illyrians supplied the Greeks with cattle and slaves, often in exchange for salt. Grecian exiles found their way into Illyria, and Grecian myths became localized there. After the death of Alexander the Great most of the tribes recovered their independence, but their piracies gave umbrage to the Romans. The Roman ambassadors who protested against their depredations were murdered by the Illyrian queen Teuta. The first Illyrian war was commenced in 230 B. C, and the queen was obliged in 229 to make peace by the surrender of part of her dominions. The second war, commenced by Demetrius of Pharos, the guardian of the Illyrian prince Pineus, was successfully terminated by the consul L. AEmilius Paulus in 219. Pleuratus, the successor of Pineus, cultivated the friendship of the Romans, but his son Gentius formed an alliance with Perseus, king of Macedon. He was conquered in the same year as Perseus, and Illyria as well as Macedon became subject to Rome (168). In the new organization under Constantine, Illyricum was one of the great divisions of the empire, and was divided into Occidentale, including Illyricum proper, Pan-nonia, and Noricum, and Orientale, comprising Dacia, Moesia, Macedonia, and Thrace. On the fall of the western empire (A. D. 476) it remained a part of the eastern.

About two centuries later the Slavic settlers from northern Europe separated themselves from the Byzantine government, and laid the foundation of the governments of Croatia and Dalmatia. At the end of the 11th century some portions of the Illyrian territory were taken by Venice and Hungary. About a century later the kingdom of Rascia was created, out of which Servia and Bosnia were subsequently formed. Dalmatia passed successively through the hands of the Venetians, Hungarians, and Turks. Venice retained only a small portion of Dalmatia, while Hungary kept Slavonia and part of Croatia. Austria obtained Dalmatia and adjacent islands by the treaty of Campo Formio in 1797. - The name Illyria, which had gradually disappeared, was revived in 1809 by the organization of the Illyrian provinces by Napoleon, comprising the territories of Carniola, Carinthia, Istria, part of Croatia, Dalmatia, Ragusa, and a military district, with a population of 1,275,000. After the fall of Napoleon they were reunited to the Austrian government, which in 1816 raised Illyria to the nominal dignity of a kingdom. It embraced the duchies of Carniola, Carinthia, Friuli, and Istria, the Hungarian Coastland, part of Croatia, and the islands in the gulf of Quarnero, having an area of about 11,000 sq. m.

The Coastland and Croatia were separated from it in 1822, and reunited with Hungary, where they have formed since 1849 part of Croatia and Slavonia. The kingdom was dissolved in the same year into the crownlands of Carinthia, Carniola, and the Littorale. The Illyrian language is one of the southern branches of the Slavic family of languages. (See Servian Language and Literature.)