Thracia or Thrace is the ancient name given to the southeastern Balkan region, the land inhabited by the Thracians. Thrace was ruled by the Odrysian kingdom during the Classical and Hellenistic eras, and briefly by the Greek Diadochi ruler Lysimachus, but became a client state of the late Roman Republic and early Roman Empire as the Sapaean kingdom. Roman emperor Claudius annexed the kingdom as a Roman province in 46 AD.

Thrace is a geographical and historical region in Southeast Europe. Bounded by the Balkan Mountains to the north, the Aegean Sea to the south, and the Black Sea to the east, it comprises present-day southeastern Bulgaria, northeastern Greece, and the European part of Turkey, roughly the Roman Province of Thrace. Lands also inhabited by ancient Thracians extended in the north to modern-day Northern Bulgaria and Romania and to the west into Macedonia.