Vilnius ( VIL-nee-əs, Lithuanian: [ˈvʲɪlʲnʲʊs] (listen); previously known in English as Vilna, see also other names) is the capital and largest city of Lithuania, with a population of 625,349 (according to the state register) or 630,885 (according to the municipality of Vilnius) as of 2023. The population of Vilnius's functional urban area, which stretches beyond the city limits, is estimated at 718,507 (as of 2020), while according to the Vilnius territorial health insurance fund, there were 753,875 permanent inhabitants as of November 2022 in Vilnius city and Vilnius district municipalities combined. Vilnius is situated in southeastern Lithuania and is currently the largest city in the Baltic states. It is the seat of Lithuania's national government and the Vilnius District Municipality.

Vilnius is known, among other things, for the architecture of its Old Town, one of the largest and best preserved old towns in northern, eastern, and central Europe, declared a UNESCO World Heritage Site in 1994. Architectural style Vilnian Baroque is named after the city, which is the largest Baroque city north of the Alps, and the farthest one to the east.

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 as one of the 25 of fDi's Global Cities of the Future.