Lithuania, officially the Republic of Lithuania, is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea, bordered by Latvia to the north, Belarus to the east and south, Poland to the south, and the Russian semi-exclave of Kaliningrad Oblast to the southwest, with a maritime border with Sweden to the west. Lithuania covers an area of 65,300 km2 (25,200 sq mi), and has a population of 2.9 million. Its capital and largest city is Vilnius; other major cities include Kaunas, Klaipėda, Šiauliai and Panevėžys. Lithuanians are the titular nation, belong to the ethnolinguistic group of Balts, and speak Lithuanian. For millennia, the southeastern shores of the Baltic Sea were inhabited by various Baltic tribes. In the 1230s, Lithuanian lands were united for the first time by Mindaugas, who formed the Kingdom of Lithuania on 6 July 1253. Subsequent expansion and consolidation resulted in the Grand Duchy of Lithuania, which by the 14th century was the largest country in Europe. In 1386, the grand duchy entered into a de facto personal union with the Crown of the Kingdom of Poland. The two realms were united into the Polish-Lithuanian Commonwealth in 1569, forming one of the largest and most prosperous states in Europe.