Union of Transylvania with Romania in the context of "Unification of Moldavia and Wallachia"

In Romanian historiography, the Great Union (Romanian: Marea Unire) or Great Union of 1918 (Marea Unire din 1918) was the series of political unifications the Kingdom of Romania had with several of the Romanian historical regions, starting with Bessarabia on 27 March 1918, continuing with Bukovina on 28 November 1918 and finalizing with Transylvania (on its broad meaning) on 1 December 1918 with the declaration of the union of this region with Romania during an assembly at the city of Alba Iulia. Romanians also consider several other events as preludes to the Great Union, such as the unification of Moldavia and Wallachia (also known as the Little Union, Mica Unire) in 1859 or the independence of the country and the annexation of Northern Dobruja in 1878, and also the occupation of Transylvania and Moldavia by the Prince of Wallachia, Michael the Brave, in 1600.

Today, the Great Union has an important meaning in Romania, and it is commemorated in the Great Union Day, the national day of the country, every 1 December. The centenary of the Great Union on 1 December 2018 was widely celebrated in Romania, with military parades at cities like Alba Iulia and Bucharest to which many people (up to 550,000, 100,000 of them in Alba Iulia alone), including the President of Romania Klaus Iohannis, attended. The centenary was also celebrated in Moldova, where more than 100 localities and 3 districts declared unification with Romania.

The Day of the Unification of the Romanian Principalities (Romanian: Ziua Unirii Principatelor Române) or, unofficially, the Little Union Day (Romanian: Ziua Micii Uniri), is a public holiday of Romania celebrated every 24 January to commemorate the unification of the Romanian Principalities (Moldavia and Wallachia), also known as the "Little Union", on 24 January 1859 under prince Alexandru Ioan Cuza. This event is deemed as important as it is considered the first step towards the goal of achieving a unitary Romanian state, something that is considered to have been achieved on 1 December 1918, when the Romanian National Assembly declared the union of Transylvania, Banat, Crișana, and Maramureș with the Kingdom of Romania.

The Day of the Unification of the Romanian Principalities was first adopted by the Senate on 2 June 2014 and later by the Chamber of Deputies on 3 December of the same year. The holiday became official when a few days later Romanian President Traian Băsescu signed a decree promulgating it on 16 December. Thus, Law No. 171/2014 dictates that, on 24 January, central and local authorities can provide material and logistical support to artistic and cultural events dedicated to this day. Since 2016, the observance is a non-working day in Romania.

Alba Iulia (Romanian pronunciation: [ˌalba ˈjuli.a] ; German: Karlsburg or Carlsburg, formerly Weißenburg [ˈvaɪsn̩bʊʁk] ; Hungarian: Gyulafehérvár [ˈɟulɒfɛɦeːrvaːr]; Latin: Apulum) is a city that serves as the seat of Alba County in the west-central part of Romania. Located on the river Mureș in the historical region of Transylvania, it has a population of 64,227 (as of 2021).

During ancient times, the site was the location of the Roman camp Apulum. Since the High Middle Ages, the city has been the seat of Transylvania's Roman Catholic diocese. Between 1526 and 1570 it was the capital of the Eastern Hungarian Kingdom from which the Principality of Transylvania emerged by the Treaty of Speyer in 1570 and it was the capital of the Principality of Transylvania until 1711. At one point it also was a center of the Eastern Orthodox Metropolitan of Transylvania with suffragan to Vad diocese. On 1 December 1918, the Union of Transylvania with Romania was declared in Alba Iulia, and Romania's King Ferdinand I and, in 1922 Queen Marie were crowned in the Alba Iulia Orthodox Cathedral.

The Great National Assembly of Alba Iulia (Romanian: Marea Adunare Națională de la Alba Iulia) was an assembly held on 1 December 1918 in the city of Alba Iulia in which a total of 1,228 delegates from several areas inhabited by ethnic Romanians declared the union of Transylvania with Romania. It was summoned by the Romanian National Council. Regular ethnic Romanian civilians were also called to participate, and these came from all regions inhabited by Romanians; in total, the assembly was attended by some 100,000 people. The union of Transylvania with Romania was declared with the adoption of the Declaration of Alba Iulia (ro) during the assembly.

Although the assembly was announced for 1 December, debates on Transylvania's accession into Romania between prominent representatives of the Romanian National Central Council started already on 30 November. At the debate, chaired by Ștefan Cicio Pop, the present social democrats, including Ioan Flueraș, argued in favour of autonomy for Transylvania within Greater Romania, while the majority of nationalists and representatives of expatriates argued against autonomy and in favour of unconditional annexation.

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.

The Coronation Cathedral (Romanian: Catedrala Încoronării), dedicated to the Holy Trinity and the Holy Archangels Michael and Gabriel, is a Romanian Orthodox cathedral located at 16 Mihai Viteazul Street, Alba Iulia, Romania. Built soon after and in commemoration of the Union of Transylvania with Romania, it is the seat of the Romanian Orthodox Archdiocese of Alba Iulia.

Iuliu Maniu (Romanian pronunciation: [ˈjulju maˈni.u] ; 8 January 1873 – 5 February 1953) was a Romanian lawyer and politician. He was a leader of the National Party of Transylvania and Banat before and after World War I, playing an important role in the Union of Transylvania with Romania.

Maniu served as Prime Minister of Romania for three terms during 1928–1933, and, with Ion Mihalache, co-founded the National Peasants' Party. Arrested by the ascendant communist authorities in 1947 as a result of the Tămădău affair, he was convicted of treason in a show trial and sent to Sighet Prison, where he died six years later.