Vilnius ( VIL-nee-əs, Lithuanian: [ˈvʲɪlʲnʲʊs] ; previously known in English as Vilna, see other names) 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.

Vilnius is notable for the architecture of its Old Town, considered one of the largest and best-preserved old towns of 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 easternmost Baroque city and the largest north of the Alps.

The city was already noted for its multicultural population 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 centers in Europe. Its Jewish influence has led to its nickname "the Jerusalem of Lithuania". Napoleon called it "the Jerusalem of the North" as he passed through in 1812.

In 2009, Vilnius was the European Capital of Culture, together with Linz in Austria. In 2021, Vilnius was named one of fDi's 25 Global Cities of the Future. Vilnius is considered one of the major world financial centres, ranked 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).