The Act of the Re-Establishment of the State of Lithuania or Act of March 11 (Lithuanian: Aktas dėl Lietuvos nepriklausomos valstybės atstatymo) was an independence declaration by the Lithuanian Soviet Socialist Republic adopted on March 11, 1990. Signed by all members of the Supreme Soviet of the Lithuanian SSR, the act emphasized restoration and legal continuity of the interwar-period Lithuania, which was occupied by the USSR and lost independence in June 1940. It was the first time that a Union Republic declared independence from the dissolving Soviet Union.

After the partitions of the Polish–Lithuanian Commonwealth in the 18th century, Lithuania was part of the Russian Empire. In the aftermath of the Russian Revolution of 1917, the Council of Lithuania, chaired by Jonas Basanavičius, proclaimed the Act of Independence of Lithuania on February 16, 1918. Lithuania enjoyed independence for two decades. In August 1939, Soviet Union and Nazi Germany signed the Molotov–Ribbentrop Pact dividing Eastern Europe into spheres of influence. The Baltic states (Lithuania, Latvia, and Estonia) were assigned to Russia and subsequently were occupied in June 1940 and converted into soviet socialist republics. The Soviet authorities undertook Sovietization policies: nationalization of all private property, collectivization of agriculture, suppression of the Catholic Church, and imposition of totalitarian control. The armed anti-Soviet partisans were liquidated by 1953. Approximately 130,000 Lithuanians, dubbed "enemies of the people", were deported into Siberia (see June deportation and March deportation). After the death of Joseph Stalin in 1953, Soviet Union adopted de-Stalinization policies and ended mass persecutions. Nonviolent resistance continued both in Lithuania and among Lithuanian diaspora. These movements were secret, illegal, and more focused on social issues, human rights, and cultural affairs rather than political demands.