Thessaly, a historic region and ancient district of Greece. The most northerly Greek district, it lay east of Epirus and south of Macedonia. The Vale (valley) of Tempe, a major pass between Macedonia and Greece, and Mount Olympus, legendary home of the Greek gods, are in Thessaly.

The region was settled in ancient times by the Aeolians, an ancient Greek people who formed a branch of the Achaeans. According to legend, it was the home of the hero Achilles. In about 1100 B.C., the Aeolians were pushed out by the Thessali (a branch of the Dorian Greeks), who invaded and settled the region, to which they gave their name. They became famous for their horsemanship and were valued allies in the constant wars between the Greek city-states.

Thessaly came under control of Macedonia in 352 B.C. and of Rome in 197 B.C. It was the site of the final battle in the civil wars of the Roman Republic when Caesar defeated Pompey at Pharsalus in 48 B.C.