Great Union in the context of "Greater Romania"

The unification of Moldavia and Wallachia (Romanian: Unirea Moldovei și Țării Românești), also known as the unification of the Romanian Principalities (Romanian: Unirea Principatelor Române) or as the Little Union (Romanian: Mica Unire), happened in 1859 following the election of Alexandru Ioan Cuza as prince of both the Principality of Moldavia and the Principality of Wallachia. A potential unification between the two principalities, which shared a common Romanian ethnicity, language, and culture, had not been favored by the great powers for a long time, although it was accepted by them once it happened. The unification of these two states began a political struggle in the new country (the United Principalities of Moldavia and Wallachia) to find out which of the two regions would obtain "supremacy" and met some opposition in Moldavia by the so-called "separatists".

Nowadays, in Romania, the unification of Moldavia and Wallachia is regarded as a prelude to the Great Union, a name used in Romanian historiography to refer to the unifications of Romania with the regions of Bessarabia, Bukovina, and Transylvania in 1918 during or following the end of World War I. It is also commemorated every 24 January through the Day of the Unification of the Romanian Principalities in both Romania and Moldova.

Great Union Day (Romanian: Ziua Marii Uniri; also called Unification Day or National Day) is a Romanian national holiday celebrated on 1 December to mark the 1918 Great Union (the unification of Transylvania, Bassarabia, and Bukovina with the Romanian Kingdom). The holiday was declared after the Romanian revolution and commemorates the Great National Assembly of the delegates of ethnic Romanians held in Alba Iulia, who declared the Union of Transylvania with Romania.

Until the abolition of the Romanian monarchy in 1947, the national holiday was observed on 10 May, which had a double meaning as it was the date on which the future King Carol I first set foot on Romanian soil in 1866 and on which he later ratified Romania's Declaration of Independence from the Ottoman Empire in 1877. During the communist regime from 1947 to 1989, the national holiday was observed on 23 August (Liberation from Fascist Occupation Day) to mark the 1944 overthrow of Ion Antonescu's government by King Michael I, with parades held in Charles de Gaulle Square (then called Stalin Square and later Aviators' Square). In 1990, the holiday's date was moved to 1 December to match the date of the Great Union.

In 2018, over a hundred localities in Moldova and dozens in Romania issued symbolic declarations of unification (Romanian: declarații de unire, sg.: declarație de unire) with the other country. Such declarations were also issued by some Moldovan districts and Romanian counties (which are respectively each country's first-level administrative divisions), members of the Moldovan and Romanian diasporas and other entities.

A movement for the unification of Moldova and Romania exists in both countries. Both share a common Romanian language, an Eastern Orthodox faith and strong cultural and historical connections. Supporters of the movement look back on the union of Bessarabia with Romania on 27 March 1918, Bessarabia being a region corresponding up to a point with modern Moldova. As the regions of Bukovina and Transylvania also united with Romania in 1918, with the three unifications being collectively known as the Great Union (Romanian: Marea Unire) among Romanians, 2018 was a symbolic year for unionists and nationalists, celebrated as the centenary of the Great Union.