Soviet–Lithuanian Non-Aggression Pact

Flag of the USSR (1936-1955).svg Sergey Alexandrovsky Flag of Lithuania.svg Mykolas Sleževičius Flag of Lithuania.svg Jurgis Baltrušaitis

• Soviet Union
• Lithuania}} Soviet–Lithuanian Non-Aggression Pact (Lithuanian: Lietuvos–SSRS nepuolimo sutartis) was a non-aggression pact, signed between the Soviet Union and Lithuania on September 28, 1926. The pact confirmed all basic provisions of the Soviet–Lithuanian Peace Treaty of 1920. The Soviet Union continued to recognize Vilnius and Vilnius Region as Lithuanian, despite the fact that the territories were under Polish control since Żeligowski's Mutiny in 1920. It also recognized Lithuania's interests in the Klaipėda Region. In exchange, Lithuania agreed not to join any alliances directed against the Soviet Union, which meant international isolation at the time when Soviet Union was not a member of the League of Nations. Ratifications were exchanged in Kaunas on November 9, 1926, and the pact became effective on the same day. The pact was registered in the League of Nations Treaty Series on March 4, 1927.

The pact was initiated by Lithuanians who sought a new direction in the foreign policy after the Locarno Treaties.

The pact was controversial in Lithuania and its ratification by the Third Seimas on 5 November 1926 caused student protests against the "Bolshevization" of Lithuania. As one of the protests was dispersed by force, it is cited as one of the reasons for the military coup in December 1926. On April 4, 1934, it was further extended to December 31, 1944. A separate convention was signed to define "aggression" on 5 July 1933. The pact was broken on 15 June 1940 with the Soviet occupation of Lithuania.