The Kingdom of Romania was the Romanian state based on a form of parliamentary monarchy between 13 March 1881 and 30 December 1947, specified by the first three Constitutions of Romania (1866, 1923, 1938). Thus, the Kingdom of Romania began with the reign of King Carol I of Romania who gained Romanian's independence in the Romanian War of Independence, and ended with the abdication of King Michael I of Romania in 30 December 1947, imposed by the Soviet Union with the tacit and secret, implicit consent of its allies (as a result of the Yalta Conference and secret agreements). As such, it is quite distinct from the Romanian Old Kingdom, which refers strictly to the reign of King Carol I of Romania, between 14 March (O.S.) (26 May (N.S.)) 1881 and 27 September (O.S.) (10 October (N.S.)) 1914.

From 1859 to 1877, Romania evolved from a personal union of two vassal principalities (Moldavia and Wallachia) under a single prince to a full-fledged independent kingdom with a Hohenzollern monarchy. In 1918, at the end of World War I, Transylvania, Eastern Moldavia (Bessarabia), and Bukovina united with the Kingdom of Romania, resulting in a "Greater Romania". In 1940, Bessarabia, Northern Bukowina, Northern Transylvania and Southern Dobruja were ceded to the Soviet Union, Hungary and Bulgaria respectively, only Northern Transylvania being recovered after World War II ended. In 1947 the last king was compelled to abdicate and a republic ruled by the Romanian Communist Party replaced the monarchy.

Romania (ⁱ/roʊˈmeɪniə/ roh-MAY-nee-ə; dated: Roumania; or Rumania;Romanian: România [romɨˈni.a] ( listen)) is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea. Romania shares a border with Hungary and Serbia to the west, Ukraine and Moldova to the northeast and east, and Bulgaria to the south.

At 238,400 square kilometers (92,000 sq mi), Romania is the ninth largest country of the European Union by area, and has the seventh largest population of the European Union with over 19 million people. Its capital and largest city is Bucharest, the tenth largest city in the EU with about two million people.

The Kingdom of Romania emerged when the principalities of Moldavia and Wallachia were united under Prince Alexander Ioan Cuza in 1859. Independence from the Ottoman Empire was declared on 9 May 1877, and was internationally recognized the following year. At the end of World War I, Transylvania, Bukovina and Bessarabia united with the Kingdom of Romania. Greater Romania emerged into an era of progression and prosperity that would continue until World War II. By the end of the War, many north-eastern areas of Romania's territories were occupied by the Soviet Union, and Romania forcibly became a socialist republic and a member of the Warsaw Pact.