Berlin, Congress of, a meeting of European powers held in Berlin during June and July, 1878, following the Russo-Turkish war of 1877–78. Representatives of Germany, France, Italy, Austria-Hungary, Russia, Turkey, and Great Britain participated. Its purpose was to revise the Treaty of San Stefano, which Russia had forced on Turkey in March.

The Treaty of San Stefano had created a large Bulgaria with access to the Aegean Sea. Since Bulgaria was almost certain to be a Russian ally, the treaty would have increased Russia's power by giving it a route to the Mediterranean. Fearing this, the other countries of Europe threatened war.

Faced with this threat, Russia agreed to revise the treaty. The resulting Treaty of Berlin gave southern Bessarabia and part of Armenia to Russia. Montenegro, Serbia, and Romania became independent states and Bulgaria semi-independent. Austria was allowed to administer Bosnia and Herzegovina, and Great Britain received Cyprus. Russia and the Balkan states were dissatisfied with the treaty, and the tensions it created were among the causes of World War I.