The first settlement finds in the area of today's capital of the Austrian province of Carinthia, Klagenfurt am Wörthersee, date back to the Bronze Age. Excavations of a few Roman villas and graves prove that there were only isolated settlements during the Roman occupation until the sixth century.

In 1142, Count Bernhard founded the Cistercian monastery of Viktring, initiating the first extensive settlement in the region. The name Klagenfurt was first documented in monastic documents from the 1190s. In 1252, Klagenfurt was granted city rights and from the mid-1250s a castle was built to protect the inhabitants. The first church was built in the 14th century and first mentioned in a document in 1347.

During the Reformation, the entire town joined the Protestant movement. Industrialization began in Klagenfurt with the connection to the railroad network in 1863 and reached its peak with complete electrification in 1896.

After the First World War, the inhabitants decided in a referendum with a clear majority in favor of Klagenfurt remaining part of Austria.

In 1930, the world's first town twinning was established between Klagenfurt and Wiesbaden. To this day, there are regular exchanges on a social, political and cultural level.

On October 18, 1973, the city senate of the Austrian twin city visited the Hessian state capital. After a brief welcome, the members of the delegation signed the city's Golden Book.