Vilnius ( VIL-nee-əs, Lithuanian: [ˈvʲɪlʲnʲʊs] ) is the capital of and largest city in Lithuania and the most-populous city in the Baltic states. The city's estimated January 2025 population was 607,404, and the Vilnius urban area (which extends beyond the city limits) has an estimated population of 747,864.

Vilnius is notable for the architecture of its Old Town, considered one of Europe's largest and best-preserved old towns. The city was declared a UNESCO World Heritage Site in 1994. The architectural style known as Vilnian Baroque is named after the city, which is farthest to the east among Baroque cities, next to Vitebsk, Mogilev and Minsk.

The city was noted for its multicultural population during the Polish–Lithuanian Commonwealth, with contemporary sources comparing it to Babylon. Before World War II and the Holocaust, in the Second Polish Republic, Vilnius (then Wilno) was one of Europe's most important Jewish centers. Its Jewish influence had led Napoleon to compare it with Jerusalem, when he passed through in 1812. The city retains a multicultural character, with a sizable Polish population.

Vilnius was a 2009 European Capital of Culture with Linz in Austria. In 2021, the city was named one of fDi's 25 Global Cities of the Future. Vilnius is considered a global financial centre, ranked 76th globally and 29th in Europe on the Global Financial Centres Index. The city is an important center for the global fintech industry. It hosted the 2023 NATO Summit. In 2025 Vilnius was the European Green Capital. Vilnius is a member of Eurocities and the Union of Capitals of the European Union (UCEU).