Coordinates: 54°22′00″N 8°55′00″E / 54.366667, 8.916667
Oldenswort is a municipality in the district of Nordfriesland, in Schleswig-Holstein, Germany, next to the river Eider.
The founder of German sociology, Ferdinand Tönnies (1855-1936), was born here. A memorial of him has been unveiled recently.