Union of Bulgaria and Romania

Map of a Bulgarian–Romanian union had it succeeded in 1887 (top) and in the present day (bottom)

Several failed proposals were made during the 19th and 20th centuries to unify Bulgaria and Romania into a common state, under either a federation, a personal union or a confederation. Such ideas found support, especially in Bulgaria, and there were several opportunities to realize them. Proposals usually came from Bulgarians, but it was Romanians who were to hold the leading positions. These proposals ultimately failed because of cultural and political differences between the two peoples and the opposition from great powers like Austria-Hungary and especially Russia.

This idea had historical precedents: Bulgarians and Romanians had first lived together under the rule of the First Bulgarian Empire, which extended its power into areas that form part of Romania today; under the Second Bulgarian Empire, established through the cooperation of Bulgarians and Vlachs (Romanians); and under the Ottoman Empire, which defeated the Second Bulgarian Empire and conquered and ruled territories populated by Bulgarians and Romanians for centuries. During the late 18th century, a popular concept emerged in the Balkans: the federalization of the region, aimed at fighting nearby empires and solving conflicts between its peoples. The idea eventually spread in Bulgaria and Romania's predecessors (Moldavia and Wallachia), gaining some support by figures such as Georgi Sava Rakovski. After the establishment of an autonomous Bulgarian principality and the full independence of Romania in 1878, relations between the countries were enhanced and there were several Romanian nominees for the Bulgarian throne. These were King Carol I of Romania and the nobleman Gheorghe G. Bibescu, son of a former Wallachian prince. They were not taken into account in the final selection, and the eventual choice in 1879 was Alexander of Battenberg, a German prince.

Although Alexander had good relations with Romania, he was forced to abdicate in 1886 following a period of political turmoil in Bulgaria caused by Russia, which tried to exert its influence over the country. Due to this, Stefan Stambolov, who was politically anti-Russian, became leader of the regents. Stambolov tried again to establish a personal union with Romania, and negotiations were conducted. Carol I would be the head of such a state with either two separate governments or a single, united one. Though Carol I had an interest in becoming ruler of Bulgaria, Russia strongly opposed this. Russia threatened to break off diplomatic relations with Romania and to invade both Romania and Bulgaria, forcing Carol I to abandon the possibility. Afterwards, Ferdinand of Saxe-Coburg and Gotha was elected Prince of Bulgaria in June 1887. New approaches to effect a union were attempted decades later in the communist era, especially by Georgi Dimitrov, but the Soviet Union strongly rejected them. Joseph Stalin, its leader, deemed the proposal unthinkable.

A Bulgarian–Romanian union was never established. The disapproval of several great powers, the differences in the Bulgarians' and the Romanians' national goals and the lack of actual interest or even opposition between these peoples, added to the hostile environment of the region in which they lived, prevented it. The idea of the federalization of the Balkans, which had great support in its time, diminished across the region after the conflicts at the beginning of the 20th century that occurred throughout Europe and, later, the violent breakup of Yugoslavia. Despite all this, the European Union, of which Bulgaria and Romania have been members since 2007, puts democratic values and pluralistic visions for European integration on the horizon of the Balkans, which has led to an idea within the academic world that a new federation proposal could emerge in the region as a result of all of this.