The Social Democratic Party of Lithuania is a centre-left and social democratic political party in Lithuania. Founded as an underground Marxist organisation in 1896, it is the oldest extant party in Lithuania. During the time of the Soviet Union, the party went into exile, emerging once again in Republic of Lithuania in 1989.

The Seimas of the Republic of Lithuania, or simply the Seimas, is the unicameral legislative body of the Republic of Lithuania. The Seimas constitutes the legislative branch of government in Lithuania, enacting laws and amendments to the Constitution, passing the budget, confirming the Prime Minister and the Government and controlling their activities.