Bulgaria (Bulgarian: България, transliterated: Balgariya,[1] pronounced IPA: [bəlˈgarija]), officially the Republic of Bulgaria (Република България, Republika Balgariya, pronounced IPA: [rɛˈpubliˌka bəlˈgarija], a state in Southeastern Europe, borders on five other countries: Romania to the north (mostly along the River Danube), Serbia and the Republic of Macedonia to the west, and Greece and Turkey to the south. The Black Sea defines the extent of the country to the east.

Bulgaria comprises the classical regions of Moesia, Thrace, and Macedonia. Old European culture within the territory of present-day Bulgaria started to produce golden artifacts by the fifth millennium BCE.[4]

The country preserves the traditions (in ethnic name, language, and alphabet) of the First Bulgarian Empire (632/681 – 1018), which at times covered most of the Balkans and spread its alphabet, literature and culture among the Slavic and other peoples of Eastern Europe. Centuries later, with the decline of the Second Bulgarian Empire (1185 – 1396/1422), the country came under Ottoman rule for nearly five centuries. The Russo-Turkish War of 1877-1878 led to the re-establishment of a Bulgarian state as a constitutional monarchy in 1878, with the Treaty of San Stefano marking the birth of the Third Bulgarian Kingdom. After World War II, Bulgaria became a communist state and part of the Eastern Bloc. In 1990, after the Revolutions of 1989, the Communist party gave up its monopoly on power and Bulgaria transitioned to democracy and free-market capitalism.

Currently Bulgaria functions as a parliamentary democracy under a unitary constitutional republic. A member of the European Union since 2007 and of NATO since 2004, it has a population of approximately 7.7 million, with Sofia as its capital and largest city.