Carol I (20 April 1839 – 27 September (O.S.) / 10 October (N.S.) 1914), born Prince Karl of Hohenzollern-Sigmaringen was the ruler of Romania from 1866 to 1914. He was elected ruling prince (Domnitor) of the Romanian United Principalities on 20 April 1866 following the overthrow of Alexandru Ioan Cuza by a palace coup. Following the defeat of the Ottoman Empire in the Russo-Turkish War, he declared Romania a sovereign nation in 1878 (the country had been under the nominal suzerainty of the Ottoman Empire until then). He was proclaimed King of Romania on 26 March [O.S. 14 March] 1881. He was the first ruler of the Hohenzollern-Sigmaringen dynasty, which ruled the country until the proclamation of a republic in 1947.
During his reign, he personally led Romanian troops during the Russo-Turkish War and assumed command of the Russo/Romanian army during the siege of Plevna. The country achieved full independence from the Ottoman Empire (Treaty of Berlin, 1878) and acquired the Cadrilater from Bulgaria in 1913. Domestic political life, still dominated by the country's wealthy landowning families organised around the rival Liberal and Conservative parties, was punctuated by two widespread peasant uprisings, in Wallachia (the southern half of the country) in April 1888 and in Moldavia (the northern half) in March 1907.
He married Elisabeth of Wied in Neuwied on 15 November 1869. They only had one daughter, Maria, who died aged three.
Carol never produced a male heir, leaving his elder brother Leopold next in line to the throne. In October 1880 Leopold renounced his right of succession in favour of his son William, who in turn surrendered his claim six years later in favour of his younger brother, the future king Ferdinand.