Lithuania is located in Northern Europe. It covers an area of 65,200 km². The country lies between latitudes 53° and 57° N, and mostly between longitudes 21° and 27° E (part of the Curonian Spit lies west of 21°). It has around 99 kilometres (61.5 mi) of sandy coastline, of which only about 38 kilometres (24 mi) face the open Baltic Sea and which is the shortest among the Baltic Sea countries; the rest of the coast is sheltered by the Curonian sand peninsula. Lithuania's major warm-water port, Klaipeda, lies at the narrow mouth of the Curonian Lagoon (Lithuanian: Kuršiu marios), a shallow lagoon extending south to Kaliningrad. The main and largest river, the Nemunas River, and some of its tributaries carry international shipping.

Lithuania lies at the edge of North European Plain. Its landscape has been smoothed by the glaciers of the last ice age. Lithuania's terrain is an alternation of moderate lowlands and highlands; its maximum elevation is Aukštojas Hill at 294 metres (965 ft) in the eastern part of the country. The terrain features numerous lakes, Lake Vištytis for example, and wetlands; a mixed forest zone covers nearly 33% of the country. The climate ranges between maritime and continental, with wet, moderate winters and mildly hot summers.

After a re-estimation of the boundaries of the continent of Europe in 1989, Jean-George Affholder, a scientist at the Institut Géographique National (French National Geographic Institute) determined that the Geographic Centre of Europe is located at 54°54'N 25°19'E. The method used for calculating this point was that of the centre of gravity of the geometrical figure of Europe. This point is located in Lithuania, specifically 26 kilometres (16 mi) north of its capital city, Vilnius.

Lithuania is the largest of the three Baltic states. It is situated along the southeastern shore of the Baltic Sea, to the east of Sweden and Denmark. It borders Latvia to the north, Belarus to the east and south, Poland to the south, and Kaliningrad Oblast (a Russian exclave) to the southwest. Lithuania has an estimated population of 3 million as of 2013, and its capital and largest city is Vilnius. The Lithuanians are a Baltic people, and the official language, Lithuanian, is one of only two living languages (together with Latvian) in the Baltic branch of the Indo-European language family.

For centuries, the southeastern shore of the Baltic Sea was inhabited by various Baltic tribes. In the 1230s the Lithuanian lands were united by Mindaugas, the King of Lithuania, and the first unified Lithuanian state, the Kingdom of Lithuania, was created on 6 July 1253. During the 14th century, the Grand Duchy of Lithuania was the largest country in Europe: present-day Lithuania, Belarus, Ukraine, and parts of Poland and Russia were the territories of the Grand Duchy. With the Lublin Union of 1569, Lithuania and Poland formed a voluntary two-state union, the Polish-Lithuanian Commonwealth. The Commonwealth lasted more than two centuries, until neighboring countries systematically dismantled it from 1772 to 1795, with the Russian Empire annexing most of Lithuania's territory.

As World War I neared its end, Lithuania's Act of Independence was signed on 16 February 1918, declaring the establishment of a sovereign State of Lithuania. Starting in 1940, Lithuania was occupied first by the Soviet Union and then by Nazi Germany. As World War II neared its end in 1944 and the Germans retreated, the Soviet Union reoccupied Lithuania.

On 11 March 1990, a year before formal break-up of the Soviet Union, Lithuania became the first Soviet republic to declare the restoration of independent State of Lithuania.

Lithuania is a member of the European Union, the Council of Europe, a full member of the Schengen Agreement and NATO. It is also a member of the Nordic Investment Bank, and part of Nordic-Baltic cooperation of Northern European countries. The United Nations Human Development Index lists Lithuania as a "very high human development" country. Lithuania has been among the fastest growing economies in the European Union and is ranked 17th in the world in the Ease of Doing Business Index.