Bessarabia (; , Bessarabiya) is a historical region in Eastern Europe, bounded by the Dniester river on the east and the Prut river on the west. The bulk of Bessarabia is currently part of Moldova, whereas the northernmost regions, as well as the southern regions bordering the Black Sea (Budjak), are part of Ukraine.
In the aftermath of the Russo-Turkish War, 1806-1812, and the ensuing Peace of Bucharest, the eastern parts of the Principality of Moldavia, an Ottoman vassal, along with some areas formerly under direct Ottoman rule, were ceded to Imperial Russia. The acquisition was among the Empire's last territorial increments to take place in Europe (the last being Congress Poland, integrated into the Empire between 1815 and 1867). The newly acquired territories were organised as the Governorate of Bessarabia, adopting a name previously used for the southern plains, between the Dniester and the Danube rivers. Following the Crimean War, in 1856, the southern areas of Bessarabia were returned to Moldavian rule; Russian rule was restored over the whole of the region in 1878, when Romania, the result of Moldavia's union with Wallachia, was pressured into exchanging those territories for the Dobruja.
In 1917, in the wake of the Russian Revolution, the area constituted itself as the Moldavian Democratic Republic, an autonomous republic part of a proposed federative Russian state. Bolshevik agitation in late 1917 and early 1918 resulted in the intervention of the Romanian Army, ostensibly to pacify the region. Soon after, the parliamentary assembly declared independence, and then union with the Kingdom of Romania. The legality of these acts was however disputed, most prominently by the Soviet Union, which regarded the area as a territory occupied by Romania.
In 1940, after securing the assent of Nazi Germany through the Molotov-Ribbentrop Pact, the Soviet Union pressured Romania into withdrawing from Bessarabia, allowing the Red Army to occupy the region. The area was formally integrated into the Soviet Union: the core joined parts of the Moldavian ASSR to form the Moldavian SSR, while territories inhabited by Slavic majorities in the north and the south of Bessarabia were transferred to the Ukrainian SSR. Axis-aligned Romania briefly recaptured the region in 1941, during the Nazi invasion of the Soviet Union, but lost it in 1944, as the tide of war changed. In 1947, the Soviet-Romanian border along the Prut was internationally recognised by the Paris Treaty that ended World War II.
During the process of the dissolution of the Soviet Union, the Moldavian and Ukrainian SSRs proclaimed their independence in 1991, becoming the modern states of Moldova and Ukraine, while preserving the existing partition of Bessarabia. Following a short war in the early 1990s, Transnistria proclaimed itself the Pridnestrovian Moldavian Republic, separate from the government of the Republic of Moldova, extending its authority also over the municipality of Bender in Bessarabia. Part of the Gagauz-inhabited areas in the southern Bessarabia was organised in 1994 as an autonomous region within Moldova.
Bessarabia is a historical region and province.