Kaunas (; Lithuanian: [ˈkɐʊˑnɐs] (listen); previously known in English as Kovno, also see other names) is the second-largest city in Lithuania after Vilnius and an important centre of Lithuanian economic, academic, and cultural life. Kaunas was the largest city and the centre of a county in the Duchy of Trakai of the Grand Duchy of Lithuania and Trakai Palatinate since 1413. In the Russian Empire, it was the capital of the Kaunas Governorate from 1843 to 1915.

During the interwar period, it served as the temporary capital of Lithuania, when Vilnius was seized and controlled by Poland between 1920 and 1939. During that period Kaunas was celebrated for its rich cultural and academic life, fashion, construction of countless Art Deco and Lithuanian National Romanticism architectural-style buildings as well as popular furniture, the interior design of the time, and a widespread café culture. The city interwar architecture is regarded as among the finest examples of European Art Deco and has received the European Heritage Label. It contributed to Kaunas being named as the first city in Central and Eastern Europe to be designated as a UNESCO City of Design. Kaunas was selected as the European Capital of Culture for 2022, together with Esch-sur-Alzette, Luxembourg and Novi Sad.

The city is the capital of Kaunas County, and the seat of the Kaunas city municipality and the Kaunas District Municipality. It is also the seat of the Roman Catholic Archdiocese of Kaunas. Kaunas is located at the confluence of the two largest Lithuanian rivers, the Nemunas and the Neris, and is near the Kaunas Reservoir, the largest body of water in the whole of Lithuania.

As defined by Eurostat, the population of Kaunas functional urban area, is estimated at 383,764 (as of 2017), while according to statistics of Kaunas territorial health insurance fund, there are 447,946 permanent inhabitants (as of 2022) in Kaunas and Kaunas district municipalities combined.