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 (Northern Thrace), northeastern Greece (Western Thrace), and the European part of Turkey (East Thrace), roughly the Roman Province of Thrace.

Thrace, Ancient and modern region, southeastern Balkan Peninsula. Its borders have varied at different periods. In ancient Greek times it was bounded by the Danube River, the Aegean Sea, and the Black Sea. Modern Thrace corresponds to southern Bulgaria, the Greek province of Thrace, and European Turkey, including the Gallipoli peninsula.

Modern-day Thrace consists of the southeastern regions of Bulgaria, northwestern Greece, and the parts of Turkey that separate the Black Sea from the Sea of Marmara.