The Ukrainian Soviet Socialist Republic (Ukrainian SSR; ; ; see "Name" section below), commonly referred to as Ukraine or Soviet Ukraine, was a sovereign Soviet socialist state and one of the fifteen constituent republics of the Soviet Union from its inception in 1922 to its breakup in 1991. For most of its existence, it was economically and politically the second-most powerful republic of the Soviet Union, behind only the Russian Soviet Federated Socialist Republic.
Although the Ukrainian SSR was a founding member of the United Nations, its foreign affairs were tightly controlled by the Kremlin. Upon the Soviet Union's dissolution and perestroika, the Ukrainian SSR was transformed into the modern nation-state of Ukraine, although Ukraine's new constitution was only ratified on 28 June 1996.
Throughout its 72-year history, the republic's borders changed many times, with a significant portion of what is now Western Ukraine being annexed by Soviet forces in 1939 and the addition of formerly Russian Crimea in 1954. From the start, the eastern city of Kharkiv served as the republic's capital. However, in 1934, the seat of government was subsequently moved to the city of Kiev, which remained the capital of newly independent Ukraine.
Geographically, the Ukrainian SSR was situated in Eastern Europe to the north of the Black Sea, bordered by the Soviet republics of Moldova, Belarus, and Russia. The Ukrainian SSR's border with Czechoslovakia formed the Soviet Union's western-most border point. With the Soviet Census of 1989, the republic's population consisted of 51,706,746 inhabitants, although the population would fall sharply after the breakup of the Soviet Union.