Lithuania occupies 65,300 square kilometers in the eastern Baltic region of Europe, bordered by Latvia to the north, Belarus to the east and south, Poland to the southwest, and Russia's Kaliningrad Oblast to the west. The Baltic Sea forms the western boundary along a coastline that extends 99 kilometers. The country's topography is overwhelmingly shaped by glaciation during the Weichselian glaciation, which retreated approximately 12,000 years ago, leaving behind a terrain defined by moraines, terminal ridges, eskers, and over 2,800 lakes. The highest point is Aukštojas Hill at 294 meters above sea level, located in the Aukštaitija region near the southeastern border with Belarus. The lowest point is sea level along the Baltic coast. The average elevation across Lithuania is 110 meters, making it one of Europe's flattest countries by mean altitude.
The territory divides into four traditional ethnographic regions that correspond to distinct landforms. Aukštaitija occupies the northeast and includes the highest terrain, characterized by hilly moraines, dense forest cover, and concentrated lake clusters. The Aukštaitija highlands contain the Ašveja Lake at 9.78 square kilometers, the country's largest lake by surface area. Žemaitija, the northwestern region, consists primarily of flat plains punctuated by the Žemaitija highland, a moraine plateau reaching 234 meters at Medvėgalis Hill. Dzūkija in the south features extensive sandy lowlands, pine forests, and marshlands, including the Čepkeliai Marsh, which covers 11,960 hectares and represents the largest raised bog in the Baltic states. Suvalkija in the southwest consists of fertile plains and gentle hills, forming part of the Middle Lithuanian Lowland.
The Nemunas River dominates Lithuania's drainage system, flowing 475 kilometers through the country from the eastern border to the Baltic Sea at Klaipėda. The river's total length is 937 kilometers, with its source in Belarus. Major tributaries include the Neris River, which flows 234 kilometers within Lithuania and passes through Vilnius, and the Merkys River in the south. The Nemunas delta forms an intricate network of channels and wetlands before entering the Curonian Lagoon. The Neris River drains from the Aukštaitija lake district and converges with the Nemunas near Kaunas, creating a flood-prone junction that historically determined settlement patterns. The Šventoji River in the northeast flows 246 kilometers, the longest river entirely within Lithuanian territory. River ice cover typically forms in December and breaks in March, with freeze duration averaging 75 to 90 days in normal winters.
The Curonian Lagoon, called Kuršių marios in Lithuanian, extends 93 kilometers from north to south along Lithuania's western coast. The lagoon covers 1,619 square kilometers total, with Lithuania controlling the northern portion. Average depth measures 3.8 meters, and salinity ranges from 0.3 to 7 parts per thousand depending on Baltic Sea influx through the Klaipėda Strait. The strait itself is 400 meters wide and serves as Lithuania's only maritime gateway. The Curonian Spit, a 98-kilometer sand peninsula separating the lagoon from the Baltic Sea, extends from Klaipėda to Kaliningrad Oblast. Lithuania controls the northern 52 kilometers. The spit's width varies from 400 meters at its narrowest to 3.8 kilometers at its widest point. The Parnidis Dune near Nida reaches 52 meters above sea level, shifting approximately 1 to 2 meters annually due to wind patterns. The entire spit formation is estimated to be 5,000 to 6,000 years old, created by longshore sediment transport from eroded Baltic coastline to the southwest.
Lithuania's lake concentration peaks in the Aukštaitija National Park, which contains 126 lakes within its 40,570-hectare area. The park was established in 1974, making it the country's oldest national park. Lake Drūkšiai on the Lithuanian-Latvian border covers 44.79 square kilometers total area, making it the largest lake touching Lithuanian territory, though Lithuania controls only the southern portion. The deepest lake is Tauragnas at 60.5 meters, located in Aukštaitija National Park. Most Lithuanian lakes are shallow moraine-dammed basins with mean depths between 5 and 15 meters. Lake Galvė in Trakai contains 21 islands within its 3.88 square kilometers, the highest island density per surface area of any Lithuanian lake. The Ignalina Nuclear Power Plant, which operated from 1983 to 2009, drew cooling water from Lake Drūkšiai and discharged heated water back into the same lake, raising average water temperature by 3 to 5 degrees Celsius during operational years.
Forest covers 33.5 percent of Lithuania's total land area, according to 2020 data from the Lithuanian State Forest Service. This percentage has increased from 19 percent in 1945 due to active reforestation programs and agricultural land abandonment. Coniferous species dominate, with Scots pine comprising 35 percent of total forest area and Norway spruce 21 percent. Deciduous species include silver birch at 22 percent, black alder at 8 percent, and pedunculate oak at 3 percent. The Dzūkija region contains the most extensive pine forests, growing on Pleistocene sand deposits with poor soil fertility. The Čepkeliai Strict Nature Reserve in Dzūkija protects 11,960 hectares of raised bog ecosystem, characterized by sphagnum moss accumulations up to 7 meters deep. The bog's surface sits 5 to 6 meters above surrounding mineral soil level. Restrictions prohibit public access except along designated boardwalk routes.
The Žemaitija National Park, established in 1991, covers 21,720 hectares surrounding Lake Plateliai, which occupies 1,200 hectares and reaches a maximum depth of 49 meters. The park contains 26 settlements with approximately 1,900 permanent residents. Lake Plateliai formed in a glacial depression and features seven islands. The Cold War-era Soviet missile base, operational from 1962 to 1978, was located within current park boundaries and housed R-12 Dvina medium-range ballistic missiles targeting Western Europe. The base was decommissioned following the Intermediate-Range Nuclear Forces Treaty and opened as the Cold War Museum in 2012.
Lithuania's Baltic coastline consists primarily of sand beaches backed by dunes reaching 10 to 15 meters height. The coastline experiences net erosion averaging 0.5 to 1 meter per year due to wave action and reduced sediment supply from damming of coastal rivers. The beach width at Palanga varies from 40 to 70 meters depending on seasonal sand migration. Amber deposits occur in Eocene Blue Earth clay layers exposed offshore and washed onto beaches after storms. Commercial amber extraction occurs in shallow Baltic waters off Klaipėda and Palanga. The Palanga Amber Museum collection contains approximately 28,000 pieces, including specimens with insect inclusions dating from 35 to 47 million years ago.
The Ventė Cape, projecting into the Curonian Lagoon south of Klaipėda, hosts the Ventės Ragas Ornithological Station, established in 1929 by German ornithologist Tadas Ivanauskas. The station operates the oldest bird ringing program in the Baltic region, with over 2 million birds ringed since establishment. The cape's location on the East Atlantic flyway makes it a critical passage point for migratory species. Annual migration counts record 100 to 150 species passing through, with peak numbers occurring in April-May and August-October. Common crane migration peaks in early October, with daily counts exceeding 10,000 individuals. The station's ringing data contributed to establishing migration routes between breeding grounds in Scandinavia and Russia and wintering areas in Western Europe and Africa.
Lithuania's climate is transitional between maritime and continental types, classified as Dfb under the Köppen system. Average January temperature in Vilnius is minus 4.9 degrees Celsius, while average July temperature is 17.0 degrees Celsius. The coastal zone experiences moderated temperatures, with Klaipėda averaging minus 2.5 degrees Celsius in January and 17.8 degrees Celsius in July. Annual precipitation ranges from 540 millimeters in the central lowlands to 930 millimeters in the western uplands.