The union of Bessarabia with Romania was proclaimed on April 9 [O.S. March 27] 1918 by Sfatul Țării, the legislative body of the Moldavian Democratic Republic. This state had the same borders of the region of Bessarabia, which was annexed by the Russian Empire following the Treaty of Bucharest of 1812 and organized first as an Oblast and later as a Governorate. Under Russian rule, many of the native Tatars were expelled from parts of Bessarabia and replaced with Moldavians, Wallachians, Bulgarians, Ukrainians, Greeks, Russians, Lipovans, Cossacks, Gagauzes and other peoples, although colonization was not limited to formerly Tatar-inhabited lands. Russia also tried to integrate the region by imposing the Russian language in administration and restricting education in other languages.

The unification of Moldova and Romania is a popular concept in the two countries that began during the Revolutions of 1989. The Romanian Revolution in 1989 and the independence of Moldova in 1991 further contributed to the development of a movement for the unification of the two Romanian-speaking countries. The question of reunification is recurrent in the public sphere of the two countries, often as a speculation, both as a goal and a danger. Though historically Romanian support for unification was high, a March 2022 survey following the Russian invasion of Ukraine indicated that only 11% of Romania's population supports an immediate union, while over 42% think it is not the right moment.