Charles I, originally Karl Eitel Friedrich Zephyrinus Ludwig von Hohenzollern-Sigmaringen, was a German prince. He was elected prince of Romania in 1866 and crowned king in 1881. Károly was born on April 20, 1839 in Sigmaringen, Germany. During his upbringing, he studied in Dresden and Bonn, and then obtained a military education in Münster. In 1866, at the request of the Romanian government, he was elected prince of Romania (domnitor in Romanian). After the expulsion of his predecessor, Prince Alexandru Ioan Cuza, he arrived in Bucharest, where he received a warm welcome from both the people and the politicians. He married Erzsébet Wiedi on November 3, 1869, and their child, Mária, was born on September 27, 1870, but she died at the age of four. No more children were born from their marriage. He was crowned king in 1881. Due to cultural, linguistic and political differences, he wanted to abdicate in 1870, but in the end he remained on the throne. Károly made significant contributions to the modernization of Romania's industry, financial institutions and army. In 1883, he made a secret alliance with Germany and the Austro-Hungarian Monarchy. Although he was pro-German, he failed to get his country to enter the war on the side of the Central Powers in the First World War. I. During his long life, Károly did a lot for the development and modernization of Romania. The king and his wife, Elizabeth, are buried in the monastery of Curtea de Argeș. Since Károly's only child, his daughter Mária, died at the age of four, his adopted nephew, Ferdinand, ruled in favor of the succession to the throne even before the proclamation of the kingdom.

During the reign of Charles I (1866-1914), the coinage of Romania underwent significant development. From the initial chaos, when different regions minted their own money, a unified and stable monetary system gradually emerged. In 1867, the leu was introduced as the official unit of the Romanian currency. The first leut coins were made of silver and gold. Coins were minted in both bronze and copper. Paper money was put into circulation in 1870. Joining the Latin Monetary Union (1878) stabilized the value of the leu. The issuance of paper money was supervised by the Romanian National Bank (Banca Națională a României). , 10, 20, 50 and 100 leu. I. Many commemorative coins were minted during Károly's reign. These coins commemorated important historical events and persons. The most common commemorative coins depicted the portrait of the king. I. King Charles' coinage played an important role in the development of the Romanian economy. A stable monetary system facilitated trade and investment and contributed to the modernization of the Romanian economy.