Lithuanian partisans (Lithuanian: Lietuvos partizanai) were partisans who waged guerrilla warfare in Lithuania against the Soviet Union in 1944–1953. Similar anti-Soviet resistance groups, also known as Forest Brothers and cursed soldiers, fought against Soviet rule in Estonia, Latvia and Poland. An estimated total of 30,000 Lithuanian partisans and their supporters were killed. The Lithuanian partisan war lasted almost for a decade, thus becoming one of the longest partisan wars in Europe.

At the end of World War II, the Red Army pushed the Eastern Front towards Lithuania. The Soviets invaded and occupied Lithuania by the end of 1944. As forced conscription into Red Army and Stalinist repressions escalated, thousands of Lithuanians took to the forests in the countryside as a refuge. These spontaneous groups became more organized and centralized culminating in the establishment of the Union of Lithuanian Freedom Fighters in February 1948. In their documents, the partisans emphasized that their ultimate goal was the recreation of independent Lithuania. As the partisan war continued, it became clear that the West would not interfere in Eastern Europe (see Western betrayal) and the partisans had no chance of success against a far stronger opponent. Eventually, the partisans made an explicit and conscious decision not to accept any new members. The leadership of the partisans was destroyed in 1953 thus effectively ending the partisan war, though individual fighters held out until the 1960s.

Lithuania regained its independence in 1918 after the collapse of the Russian Empire. As pre-war tensions rose in Europe, Nazi Germany and the Soviet Union signed the Molotov–Ribbentrop Pact and divided Eastern Europe into spheres of influence. Subsequently, Lithuania was occupied by the Soviet Union in June 1940. The Soviets instituted Sovietization policies and repressions. In June 1941, the Soviets deported over 17,000 Lithuanians to Siberia, with most of the deportees dying in the harsh winters. When a few days Germany launched an invasion of Russia, Lithuanians organized a popular anti-Soviet uprising. Initially, the Lithuanians greeted the Germans as liberators from the repressive Soviet rule and made plans to reestablish independent Lithuania. However, the attitudes soon changed as the occupation of Lithuania by Nazi Germany continued.

Unlike Estonia and Latvia where the Germans conscripted the local population into military formations in the Waffen-SS, Lithuania boycotted German recruitment calls and never had their own Waffen-SS division. In 1944, the Nazi authorities authorized the Lithuanian Territorial Defense Force (LTDF) under General Povilas Plechavičius to combat Soviet partisans led by Antanas Sniečkus and the Polish partisans of the Home Army. The LTDF soon reached a strength of 19,500 men. The Germans, however came to see the LTDF as a nationalist threat to their occupation regime and its senior staff were arrested on May 15, 1944. General Plechavičius was deported to the Salaspils concentration camp in Latvia. However, a large proportion of the LTDF succeeded in escaping deportation to Germany and formed guerrilla units, dissolved into the countryside in preparation for partisan operations against the Soviet Army as the Eastern Front approached.

On July 1, 1944, the Lithuanian Liberty Army (Lithuanian: Lietuvos laisvės armija, LLA) declared a state of war against the Soviet Union and ordered all able-bodied members to mobilize into platoons stationed in the forests and not to leave Lithuania. The departments were replaced by two sectors – operational, called Vanagai (Hawks or Falcons; abbreviated VS), and organizational (abbreviated OS). Vanagai, commanded by Albinas Karalius (codename Varenis), were the armed fighters while the organizational sector was tasked with passive resistance, including supply of food, information, and transport to Vanagai. In the middle of 1944, the LLA had 10 000 members. The Soviets had killed 659 and arrested 753 members of the LLA by January 26, 1945. Founder Kazys Veverskis was killed in December 1944, and its headquarters were liquidated in December 1945. This represented the failure of highly centralized resistance; the organization was depended too much on Veverskis and other top commanders. In 1946 the remaining leaders and fighters of the LLA started to merge with Lithuanian partisans. In 1949 all members of the presidium of the Union of Lithuanian Freedom Fighters – captain Jonas Žemaitis-Tylius, Petras Bartkus-Žadgaila, and Bronius Liesys-Naktis ir Juozas Šibaila-Merainis – came from the LLA.

The Supreme Committee for the Liberation of Lithuania (Lithuanian: Vyriausiasis Lietuvos išlaisvinimo komitetas, VLIK) was created on November 25, 1943. VLIK published underground newspapers and agitated for resistance against the Nazis. The Gestapo arrested most influential members in 1944. After the reoccupation of Lithuania by the Soviets, VLIK moved to the West and set as its goal to maintain the non-recognition of Lithuania's occupation and dissemination of information from behind the Iron Curtain – including the information provided by the Lithuanian partisans.

Former members of the Lithuanian Territorial Defense Force, the Lithuanian Liberty Army, Lithuanian Armed Forces and Lithuanian Riflemen's Union formed the basis of Lithuanian partisans. Farmers, Lithuanian officials, students, teachers, and even pupils joined the partisans. The movement was actively supported by Lithuanian society and the Catholic church. By the end of 1945, an estimated 30 000 armed people lived in the Lithuanian forests.

The resistance in Lithuania was well organized, and uniformed guerrilla units with a chain of command were effectively able to control whole regions of the countryside until 1949. Their armaments included Czech Škoda guns, Russian Maxim heavy machine guns, assorted mortars and a wide variety of mainly German and Soviet light machine guns and submachine guns. When not directly fighting the Soviet Army or special NKVD units, they significantly delayed the consolidation of Soviet rule through ambush, sabotage, assassination of local Communist activists and officials, freeing imprisoned guerrillas, and printing underground newspapers. Captured Lithuanian Forest Brothers often faced torture and summary execution, while their relatives faced deportation to Siberia (cf. quotation). Reprisals against pro-Soviet farms and villages were harsh. The NKVD units (known by the Lithuanians as pl. stribai, from the Russian: istrebiteli – destroyers) used cruel repression to discourage further resistance, e.g. displaying executed partisans' corpses in village courtyards.