Mysia, in ancient geography, a X. W. division of Asia Minor, the boundaries of which greatly varied at different periods. In the time of the early Roman emperors it was bounded N. by the Propontis (sea of Marmora), N. E. in part by the Bithynian Olympus, S. E. by Phrygia, S. by Lydia, W. by the Aegean, and N. W. by the Hellespont (strait of Dardanelles). It thus included, among other territories, those of Troas in the northwest, and Teuthrania (which included Pergamus), as well as the Grecian coast land of Aeolis, in the southwest. Mysia was for the most part mountainous, the principal ranges within its boundaries being Mt. Ida in Troas, Mt. Temnus, which extended from the former to the borders of Phrygia, dividing the country into two unequal parts, and Mt. Olympus on the northeastern or Bithynian border. Of the principal rivers, the Caicus and Evenus flowed into the Elaitic gulf, on the S. AV. corner; the Satniois into the Aegean, N. of Cape Lectum; the Scamander and Simois, renowned in Trojan legends, into the Hellespont, near Cape Sigeum; the Grani-cus, on the banks of which Alexander the Great achieved his first victory over the Persians (334 B. C), the Aesepus, Tarsius, Maces-tus, and Rhyndacus, into the Propontis. The largest gulf was that of Adramyttium (now Adramyti) on the Aegean, opposite the island of Lesbos. Mysia is more renowned in legendary traditions than in history, the chief interest attaching to the territories of Troas, Pergamus, and the Aeolian confederacy.

Some suppose the Mysians to have been of Thracian race and immigrants from the countries south of the Danube afterward known as Mcesia, and others make them offshoots of the Lydians. Egyptologists think they can recognize their name in inscriptions of very ancient date. Having been successively under the dominion of Croesus, the Persian kings, Alexander of Macedon, his general Lysimachus, and the Se-leucida?, Mysia was assigned by the Romans, after their victory over Antiochus the Great (190), to the new kingdom of Pergamus, which had previously been formed from one of its parts, and with the whole of that kingdom was bequeathed to the Roman republic by King Attalus III., thus becoming a part of the proconsular province of Asia (133).