Lithuania is a signatory of the nuclear Non-Proliferation Treaty (NPT) and has signed and ratified the Comprehensive Test Ban Treaty (CTBT), being one of the 44 listed countries needed to sign and ratify for the CTBT to enter into force.

Lithuania was host to the world's largest nuclear reactors, at Ignalina, where two RBMK 1500 MW water-cooled graphite-moderated models are located. These were the only RBMKs of this size in operation anywhere in the former Soviet Union. Initially four reactors were planned at Ignalina but only two were completed. Construction of the third reactor was halted in 1989 due to public opposition and in 1993 dismantling of the structure began.

Ignalina was built as a regional reactor in the time of the Soviet Union and was largely operated and controlled by Russians. Following the political changes Lithuania assumed ownership of the reactors on 27th August 1991. In 1993, the reactors contributed nearly 90% of the nation's electricity, the highest share of nuclear electricity ever recorded in a country.

In February 1999 EU officials told the Lithuanian Economy Ministers that if Lithuania did not close Ignalina by 2005 then it could not begin negotiations to join the European Union. Prior to the EU summit in Helsinki in December 1999 closure dates for both units were agreed, reactor 1 by 2005 and 2 in 2009. Unit 1 was closed in December 2004.