Tiiessaly (Gr. θεσσαλία or θετταλία ), the largest political division of ancient Greece, comprising in its fullest extent the country between Thermopylae and the Cambunian mountains in one direction, and between the range of Pindus and the AEgean sea in the other, But Thessaly proper was the plain between the Cambunian mountains on the north, Ossa and Pelion on the east, Mt. Othrys on the south, and the Pindus range on the west. This plain, whose natural enclosure of mountains is broken only at the northeast by the vale of Tempe, was the most fertile region and the largest that was continuously productive in Greece, and was supposed by its inhabitants to have once been a lake, of which the lakes Nessonis (now Kara Tchai'r) and Boebeis (Karla) were the remains. It was drained by the Peneus (Se-lembria or Salamvria) and its tributaries, and was divided into two plains, which in antiquity were called Upper Thessaly and Lower Thessaly; the former embracing Thessaliotis and Hesticeotis, between AEginium in the northwest and Thaumaci in the south, and having Pharsalus for its chief city; the latter, Pelas-giotis, stretching from Mts. Olympus and Ossa on the north to Mt. Othrys and the gulf of Pagasee (now of Volo) on the south, and having Larissa as its most important town.

Thessaly proper was early divided into the four districts of Thessaliotis, Hestiasotis, Pelasgio-tis, and Phthiotis; and this division, the origin of which is sometimes ascribed to Aleuas, the founder of the Aleuadse, was continued down to a very late time. In addition to Thessaly proper, the name was extended over Malis or Malia, a narrow valley between Mts. Othrys and (Eta, through which the river Spercheus enters the Maliac gulf; and to Magnesia, a region lying along the coast and stretching S. from the vale of Tempe, and almost encircling the gulf of Pagasa3. - The Thessalians were said to have been originally emigrants from Thesprotia in Epirus, who conquered the Pelasgian inhabitants of the plain of the Peneus, which is said by Herodotus to have then been called .AEolis. During the historic period three classes inhabited the country. The first was a body of rich oligarchical proprietors, who owned most of the soil. Of these the most powerful families were the Aleuadae of Larissa, the Scopadae of Crannon, and the Creonida) of Pharsalus; the second were the subject Achaeans, Magnetes, and Perrhsebi, who retained their tribe names and separate votes in the Amphictyonic council; the third were the Penestae or serf cultivators of the soil, who could not be sold out of the country, and who kept up among themselves the relations of family and community.

These were no doubt earlier inhabitants reduced to serfdom; but whether they were Pe-lasgians or Boeotians, as Grote suggests, it is impossible to determine. The language spoken in Thessaly was AEolic Greek. The four divisions of the country formed a political union, existing rather in theory than in fact. To enforce obedience to the common authority • a chief or tagus was sometimes elected; but constant feuds between the larger cities prevented Thessaly from occupying its rightful position in Greece. The inhabitants were early engaged in a constant war with the Phocians; they joined by constraint the army of Xerxes in his invasion of Greece, but took no part in the Peloponnesian war. About 400 B. C. Pherae rose to political supremacy in Thessaly under Lycophron, who had made himself tyrant, and his successor Jason, who reduced all Thessaly to his authority, and meditated not only the conquest of Greece, but the overthrow of the Persian empire; but before he had time to mature his designs he was assassinated.

Alexander of Pherae maintained and extended his power (see PherAE); but after his death the country fell into the hands of Philip of Macedon. It formed a part of the Macedonian monarchy until the defeat of Philip V. at Cynoscephalse in 197, when it came under the Roman dominion, and the government was given to wealthy persons, who met in Larissa. - Thessaly now forms a part of the Turkish vilayet of Janina, excepting the southernmost portion, from Mt. Othrys, which he-longs to Greece. (See Phthiotis.) The chief town of Turkish Thessaly is Trikala, and of the Greek portion Lamia or Zeitun.