Carol I of Romania in the context of "Siege of Plevna"

Romania is a country located at the crossroads of Central, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to the east, and the Black Sea to the southeast. It has a mainly continental climate, and an area of 238,397 km (92,046 sq mi) with a population of 19 million people. Romania is the twelfth-largest country in Europe and the sixth-most populous member state of the European Union. Europe's second-longest river, the Danube, empties into the Danube Delta in the southeast of the country. The Carpathian Mountains cross Romania from the north to the southwest and include Moldoveanu Peak, at an altitude of 2,544 m (8,346 ft). Bucharest is the country's capital, largest urban area, and financial centre. Other major urban areas include Cluj-Napoca, Timișoara, Iași, Constanța and Brașov.

Settlement in the territory of modern Romania began in the Lower Paleolithic, later becoming the Dacian Kingdom before Roman conquest and Romanisation. The modern Romanian state was formed in 1859 with the unification of Moldavia and Wallachia under Alexandru Ioan Cuza, becoming the Kingdom of Romania in 1881 under Carol I of Romania. Romania gained independence from the Ottoman Empire in 1877, formalised by the Treaty of Berlin. After World War I, Transylvania, Banat, Bukovina, and Bessarabia joined the Old Kingdom, forming Greater Romania, which reached its largest territorial extent. In 1940, under Axis pressure, Romania lost territories to Hungary, Bulgaria, and the Soviet Union. Following the 1944 Romanian coup d'état, Romania switched sides to join the Allies. After World War II, it regained Northern Transylvania through the Paris Peace Treaties. Under Soviet occupation, King Michael I was forced to abdicate, and Romania became a socialist republic and Warsaw Pact member. After the uniquely violent Romanian revolution in December 1989, Romania began a transition to liberal democracy and a market economy.

The Kingdom of Romania (Romanian: Regatul României) was a constitutional monarchy that existed from 25 March [O.S. 13 March] 1881 with the crowning of prince Karl of Hohenzollern-Sigmaringen as King Carol I (thus beginning the Romanian royal family), until 1947 with the abdication of King Michael I and the Romanian parliament's proclamation of the Romanian People's Republic.

From 1859 to 1877, Romania evolved from a personal union of two principalities: (Moldavia and Wallachia) called the Unification of Moldavia and Wallachia also known as "The Little Union" under a single prince to an autonomous principality with a Hohenzollern monarchy. The country gained its independence from the Ottoman Empire during the 1877–1878 Russo-Turkish War (known locally as the Romanian War of Independence), after which it was forced to cede the southern part of Bessarabia in exchange for Northern Dobruja. The kingdom's territory during the reign of King Carol I, between 13 (O.S.) / 25 March 1881 and 27 September (O.S.) / 10 October 1914 is sometimes referred to as the Romanian Old Kingdom, to distinguish it from "Greater Romania", which included the provinces that became part of the state after World War I (Bessarabia, Banat, Bukovina, and Transylvania).

The United Principalities of Moldavia and Wallachia (Romanian: Principatele Unite ale Moldovei și Țării Românești), commonly called United Principalities or Wallachia and Moldavia, was the personal union of the Principality of Moldavia and the Principality of Wallachia. The union was formed on 5 February [O.S. 24 January] 1859 when Alexandru Ioan Cuza was elected as the Domnitor (Ruling Prince) of both principalities. Their separate autonomous vassalage in the Ottoman Empire continued with the unification of both principalities. On 3 February [O.S. 22 January] 1862, Moldavia and Wallachia formally united to create the Romanian United Principalities, the core of the Romanian nation state.

In February 1866, Prince Cuza was forced to abdicate and go into exile by a political coalition led by the Liberals; the German prince Karl of Hohenzollern-Sigmaringen was offered the throne and, on 22 May [O.S. 10 May] 1866 he entered Bucharest for the first time. In July the same year, a new constitution came into effect, giving the country the name of Romania; internationally, this name was used only after 1877, since at the time it shared a common foreign policy with the Ottoman Empire. Nominally, the new state remained a vassal of the Ottoman Empire. However, by this time the suzerainty of the Sublime Porte had become a legal fiction. Romania had its own flag and anthem; after 1867, it had its own currency as well.

The Romanian royal family (Romanian: Familia regală a României) constitutes the Romanian subbranch of the Swabian branch of the House of Hohenzollern (also known as the House of Hohenzollern-Sigmaringen), and was the ruling dynasty of the Kingdom of Romania, a constitutional monarchy in Central-Eastern Europe. The kingdom existed from 1881, when Carol I was proclaimed king, until 1947, when the last king, Michael I, was forced to abdicate and the Parliament proclaimed Romania a republic. Soon after, upon the establishment of the constitution of 13 April 1948, Romania became a people's republic, a state that lasted until the Romanian Revolution in 1989.

Current members of the former royal family include the daughters of the late, former King Michael of Romania. Some descendants have adopted the surname "of Romania". There are also descendants of Michael's older half-brother Carol Lambrino (also known as "Carol Hohenzollern" and "Carol Mircea Grigore of Romania" or, in Romanian, al României, on his amended, Romanian birth certificate), whose legitimacy was disputed and who were not recognised as royal during the reigns of Ferdinand, Carol II and Michael.

Prince Domnitor, in full Principe Domnitor (Romanian pl. Principi Domnitori) was the official title of the ruler of Romania between 1862 and 1881. It was usually translated as "prince regnant" in English and most other languages, and less often as "grand duke". "Domnitor" is an adjective derived from the Romanian word "domn" (lord or ruler) and, in turn, from the Latin "Dominus". The title Domn had been in use since the Middle Ages and it is also the Romanian equivalent to the Slavic Hospodar. Moldavian and Wallachian rulers had used this term for their title of authority as the head of state, while "voievod" represented the military rank as the head of the army.

The title acquired an officially recognized meaning after Moldavia and Wallachia united to form the Romanian United Principalities under Alexander John I, who had become the ruler of both states since 1859. Alexander John abdicated in 1866 and was succeeded by Carol I, who promulgated the first constitution who officially used the name Romania for the country. He held the title until 1881. When Romania was proclaimed a kingdom in March 1881, Carol became its first king.

Carol II (15 October 1893 [O.S. 3 October 1893] – 4 April 1953) was King of Romania from 8 June 1930 following a coup that deposed his son until his forced abdication on 6 September 1940. As the eldest son of King Ferdinand I, he was crown prince from the death of his granduncle, King Carol I, in 1914 until he was forced to renounce his right to the throne in 1925.

Carol's life and reign were surrounded by controversy, such as his desertion from the army during World War I. Another controversy was his marriage to Zizi Lambrino, who was not from a royal lineage. After the dissolution of his first marriage, he met Princess Helen of Greece and Denmark, daughter of King Constantine I of Greece, married her in March 1921, and later that year, they had a son, Michael. Due to his continued extramarital affair with Elena Lupescu, Carol was forced to renounce his succession rights in 1925. His father removed Carol from the royal house of Romania and he was exiled to France along with Lupescu. Michael, aged 5, inherited the throne on the death of King Ferdinand in 1927. Princess Helen divorced Carol in 1928.

The 1866 Constitution of Romania was the fundamental law that capped a period of nation-building in the Danubian Principalities, which had united in 1859. Drafted in a short time and closely modeled on the 1831 Constitution of Belgium, then considered Europe's most liberal, it was substantially modified by Prince (later King) Carol and adopted by the Constituent Assembly. The newly installed Prince then promulgated it on 13 July [O.S. 1 July] 1866. In a bold move, the constitution was drafted without input from the major powers. Notably, the framers did not even consult the Ottoman Empire even though Romania was nominally an Ottoman vassal. By then, however, the Ottoman Empire's sovereignty over Romania had long since become a legal fiction, though this only ended when Romania gained de jure independence in 1878.