Lithuania occupies 65,300 square kilometers in northeastern Europe, making it the largest of the three Baltic states by land area. The country borders Latvia to the north across a 544-kilometer frontier, Belarus to the east and south across 640 kilometers, Poland to the southwest across 104 kilometers, and Russia's Kaliningrad Oblast to the west across 261 kilometers. Lithuania's western edge meets the Baltic Sea along 99 kilometers of coastline, a relatively short maritime boundary that nonetheless provides the nation's only direct access to open waters. The capital Vilnius sits in the southeastern interior, 312 kilometers from the coast and approximately 40 kilometers from the Belarusian border, placing Lithuania's political center closer to continental Europe than to the Baltic maritime zone.
The country's topography consists almost entirely of lowlands shaped by successive glaciations during the Pleistocene epoch, with the last ice sheets retreating approximately 12,000 years ago. The highest point, Aukštojas Hill in the Aukštaitija region near the Belarusian border, reaches 294 meters above sea level, while the lowest elevations occur in the Nemunas River delta at sea level. This modest 294-meter elevation range places Lithuania among Europe's flattest countries, with approximately 75 percent of the territory lying below 200 meters elevation. The glacial legacy manifests in undulating moraine hills, particularly across Aukštaitija in the northeast and Žemaitija in the northwest, where terminal moraines deposited by retreating ice created modest ridges rarely exceeding 50 meters of local relief. Between these glacially sculpted highlands lie broad outwash plains, especially across Dzūkija in the south, where meltwater deposited extensive sand and gravel sheets that now support pine forests growing on nutrient-poor soils.
Lithuania contains approximately 6,000 lakes, most concentrated in Aukštaitija National Park where glacial processes carved kettle lakes and deposited irregular moraine topography. Lake Drūkšiai, shared with Belarus and covering 44.8 square kilometers on the Lithuanian side, ranks as the country's largest lake, though much of its 48.4-square-kilometer total area extends into Belarusian territory. The lake reaches depths of 33.3 meters, making it also Lithuania's deepest freshwater body. Aukštaitija National Park alone contains 126 lakes within its 405.7-square-kilometer protected area, a density reflecting the chaotic drainage patterns left by glacial retreat. These lakes typically possess irregular shorelines with numerous bays and peninsulas, clear waters with visibility reaching 3 to 5 meters in summer, and pH levels between 7 and 8 indicating mineral-rich glacial substrates. Lake turnover patterns follow temperate norms, with surface temperatures reaching 20 to 23 degrees Celsius in July and ice cover persisting from December through March in most years.
The Nemunas River, Lithuania's primary waterway, flows 937 kilometers from Belarus through central Lithuania to the Baltic Sea, with 475 kilometers traversing Lithuanian territory. At Kaunas, where the Neris River joins the Nemunas, the combined flow averages 678 cubic meters per second, rising to approximately 950 cubic meters per second at the delta during spring snowmelt. The Nemunas basin drains 74 percent of Lithuania's territory, creating a unified hydrological system that historically facilitated internal navigation and trade. The river's gradient averages just 0.3 meters per kilometer across Lithuanian territory, producing sluggish currents and meandering channels through broad floodplains. Spring floods, occurring typically in late March or early April when snowmelt coincides with ice breakup, historically inundated floodplains up to 5 kilometers wide, though Soviet-era channelization and the Kaunas Hydroelectric Plant, completed in 1960 with a reservoir extending 63.5 kilometers upstream, have substantially altered the river's natural flood regime. The Neris River, the Nemunas's major tributary, flows 510 kilometers with 234 kilometers in Lithuania, draining the Vilnius region before joining the Nemunas at Kaunas.
The Curonian Lagoon, separated from the Baltic Sea by the 98-kilometer Curonian Spit, constitutes one of the largest coastal lagoons in Europe at 1,619 square kilometers total area, with 413 square kilometers in Lithuanian territorial waters. The lagoon averages just 3.8 meters depth, reaching maximum depths of 5.8 meters in channels dredged for navigation. Fresh water dominates the lagoon's composition, as the Nemunas River discharges an average 678 cubic meters per second into the southern basin, creating salinity levels typically between 0.5 and 2 parts per thousand compared to the Baltic Sea's 7 to 8 parts per thousand. This freshwater dominance creates a unique brackish ecosystem supporting species adapted to low-salinity conditions. The Klaipėda Strait, a navigable channel maintained at 14 meters depth and 200 meters width, connects the lagoon to the Baltic Sea through the Curonian Spit's northern end, permitting maritime traffic to reach Klaipėda port located on the lagoon's eastern shore 8 kilometers from open sea.
The Curonian Spit itself extends 98 kilometers from Klaipėda southward to the Russian exclave of Kaliningrad Oblast, with 52 kilometers in Lithuanian territory. This narrow sand barrier ranges from 400 meters to 3,800 meters in width, formed through longshore drift processes accumulating sand transported northward along the Baltic coast by prevailing southwesterly winds and currents. The spit's western face meets the Baltic Sea along an unbroken beach backed by foredunes typically 8 to 12 meters high, while the eastern shore edges the Curonian Lagoon with lower elevations and marsh vegetation. Inland from the Baltic beach, parabolic dunes rise dramatically, with Parnidis Dune near Nida reaching 52 meters above sea level and migrating eastward at rates historically documented at 1 to 2 meters annually before stabilization efforts began in the 19th century. Deforestation during the 17th and 18th centuries, driven by timber extraction for shipbuilding and fuel, destabilized these dunes, causing sand to bury 14 villages between 1675 and 1854, documented in Prussian administrative records. Systematic pine afforestation initiated in the 1820s under Prussian administration, continuing through Lithuanian independence after 1918 and Soviet occupation from 1945 to 1990, has stabilized approximately 70 percent of the spit's dune systems, though active dune fields persist near Nida where sand movement continues under monitoring by Curonian Spit National Park authorities.
Lithuania's climate classification falls within the humid continental category, specifically the Dfb type in the Köppen system, characterized by warm summers, cold winters, and precipitation distributed relatively evenly across all months. Mean annual temperatures average 6.0 degrees Celsius in Vilnius, 6.5 degrees Celsius in Kaunas, and 7.4 degrees Celsius in Klaipėda, with the coastal location experiencing moderating maritime influence from the Baltic Sea. These national averages mask substantial seasonal extremes, particularly in the continental interior. Vilnius experiences average January temperatures of minus 4.9 degrees Celsius, with absolute minimums reaching minus 37.2 degrees Celsius as recorded on January 1, 1942, and minus 36.6 degrees Celsius on February 11, 1929. July averages in Vilnius reach 17.0 degrees Celsius, with absolute maximums of 35.6 degrees Celsius recorded on August 5, 2014, and 35.5 degrees Celsius on July 30, 1994. These temperature extremes reflect Lithuania's position at the intersection of maritime air masses originating over the Atlantic and continental air masses from the Eurasian interior, with neither influence dominating sufficiently to eliminate seasonal extremes.