The Corfu Declaration was an agreement between the prime minister of Serbia, Nikola Pašić, and the president of the Yugoslav Committee, Ante Trumbić, concluded on the Greek island of Corfu on 20 July 1917. Its purpose was to establish the method of unifying a future common state of the South Slavs living in Serbia, Montenegro and Austria-Hungary after the First World War. Russia's decision to withdraw diplomatic support for Serbia following the February Revolution, as well as the Yugoslav Committee's sidelining by the trialist reform initiatives launched in Austria-Hungary, motivated both sides to attempt to reach an agreement.

The Kingdom of Serbia was a country located in the Balkans which was created when the ruler of the Principality of Serbia, Milan I, was proclaimed king in 1882. Since 1817, the Principality was ruled by the Obrenović dynasty. The Principality, under the suzerainty of the Ottoman Empire, de facto achieved full independence when the very last Ottoman troops left Belgrade in 1867. The Congress of Berlin in 1878 recognized the formal independence of the Principality of Serbia, and in its composition Nišava, Pirot, Toplica and Vranje districts entered the South part of Serbia.