Tönning (German; Low German Tünn, Tönn or Tönnen; Danish: Tønning; North Frisian: Taning) is a town in the district of Nordfriesland in the German state of Schleswig-Holstein.

During the Great Northern War, (1700–1721), Tönning was besieged twice.

It is located on the northern bank of the Eider river, approximately eight kilometers away from its mouth at the North Sea.

Tönning is connected by a regional train with Sankt Peter-Ording to the West, and Husum to the North-East.

Tönning is also served by several bus routes.