The Great Seimas of Vilnius was a major assembly held on December 4 and 5, 1905 in Vilnius, Lithuania, then part of the Russian Empire, largely inspired by the Russian Revolution of 1905. It was the first modern national congress in Lithuania and dealt primarily not with the social issues that sparked the revolution, but with national concerns. Over 2,000 participants took part in the Seimas. The assembly made the decision to demand wide political autonomy within the Russian Empire and achieve this by peaceful means. It is considered an important step towards the Act of Independence of Lithuania, adopted on February 16, 1918, by the Council of Lithuania, as the Seimas laid the groundwork for the establishment of an independent Lithuanian state.

Vilnius is the capital of and largest city in Lithuania, and the second-most populous city in the Baltic states. As of January 2024, Vilnius' estimated population was 602,430, and the Vilnius urban area which extends beyond the city limits has an estimated population of 708,627.