Dobruja, also Dobroja or Dobrogea, historic region, south-eastern Europe, in north-eastern Bulgaria and south-eastern Romania, between the lower Danube and the Black Sea. This broad plain includes the Danube Delta in the north, and contains large areas of farmland. Major crops include cereal grains, beet, grapes, mulberries, fodder, and tobacco. The coast is covered by sandy beaches and seaside resorts. The main town is the historic port of Constanţa.

Dobruja, which is a major wildlife sanctuary, was designated a World Heritage Site in 1991. About 300 species of birds, including herons and pelicans, have been recorded in the delta. Mammals include boars, deer, and wildcats, and fish include carp, perch, and sturgeon.

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 1877-1878, 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 1912-1913 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, Constanţa and Tulcea. Area of the entire region, about 23,310 sq km (9,000 sq mi).