Vilnius ( VIL -nee-əs, Lithuanian: [ˈvʲɪlʲnʲʊs] ; previously known in English as Vilna , see other names) is the capital and largest city of Lithuania. As of July 2023, Vilnius' estimated population was 593,436. The Vilnius urban area, extending beyond the city limits, had an estimated population of 718,507 in 2020. By November 2022, there were approximately 753,875 permanent residents in Vilnius city and Vilnius district municipalities combined.

Vilnius is located in southeastern Lithuania and is the second largest city in the Baltic states (or the largest, according to the municipal statistics and the center of registers of Lithuania). It is the seat of Lithuania's national government and the Vilnius District Municipality.

Vilnius is notable for the architecture of its Old Town. Considered one of the largest and best preserved old towns in Europe, Vilnius was declared a UNESCO World Heritage Site in 1994. The architectural style known as Vilnian Baroque is named after the city, which is the largest Baroque city north of the Alps, and the easternmost one.

The city was noted for its multicultural population already in the time of the Polish–Lithuanian Commonwealth, with contemporary sources comparing it to Babylon. Before World War II and the Holocaust, Vilnius was one of the most important Jewish centres in Europe. Its Jewish influence has led to its nickname "the Jerusalem of Lithuania". Napoleon called it "the Jerusalem of the North" as he was passing through in 1812.

In 2009, Vilnius was the European Capital of Culture, together with Linz, Austria. Furthermore, in 2021, Vilnius was named one of the 25 fDi's Global Cities of the Future. Vilnius is considered one of the major world financial centres, being placed 76th globally and 29th in Europe, according to the Global Financial Centres Index. In 2023, Vilnius hosted the 2023 NATO Summit.

Vilnius is a member of Eurocities and the Union of Capitals of the European Union (UCEU).