Klagenfurt am Wörthersee, usually known as just Klagenfurt, is the capital of the federal state of Carinthia in Austria. With a population of 101,303 (1 January 2020), it is the sixth-largest city in the country. The city is the bishop's seat of the Roman Catholic Diocese of Gurk-Klagenfurt and home to the University of Klagenfurt, the Carinthian University of Applied Sciences and the Gustav Mahler University of Music.

The city is in southern Austria, midway across the nation, near the international border. It is in the lower middle of Austria, almost the same distance from Innsbruck in the west, as it is from Vienna in the northeast.

Klagenfurt is elevated 446 metres (1,463 feet) above sea level and covers an area of 120.03 square kilometres (46.34 sq mi). It is on the lake Wörthersee and on the Glan river. The city is surrounded by several forest-covered hills and mountains with heights of up to 1,000 m (3,300 ft) (for example Ulrichsberg). To the south of the city is the Karawanken mountain range, which separates Carinthia from bordering nations of Slovenia and Italy.