Dobruja, also Dobroja or Dobrogea, historic region, southeastern Europe, in northeastern Bulgaria and southeastern Romania, between the lower Danube River and the Black Sea. The region is generally fertile; major crops are cereal grains, beets, grapes, mulberries, fodder, and tobacco.

Originally part of the Roman Empire, later of the Byzantine Empire, and after the 15th century, a province of the Ottoman Empire, Dobruja was the battleground of the Russo-Turkish wars of the 18th and 19th centuries. Northern Dobruja was granted to Romania by the terms of the Treaty of Berlin following the Russo-Turkish War of 1877-78, and southern Dobruja was given to the newly created principality of Bulgaria. Ceded to Romania under the terms of the Treaty of Bucharest concluding the Balkan Wars of 1912-13 and again by the Treaty of Neuilly in 1919, southern Dobruja was returned to Bulgaria by Hitler in September 1940 (the Treaty of Craiova). After 1949 Bulgarian Dobruja was included within the provinces of Ruse and Stalin. Romanian Dobruja, a historic province, has two districts, Constanta and Tulcea. Area of the entire region, about 23,310 sq km (about 9000 sq mi).