The Dithmarscher Eiderwatt, officially the Dithmarscher Eidervorland mit Watt ("Dittmarschen Eider Foreland and Watt"), is a nature reserve in the district of Dithmarschen in the north German state of Schleswig-Holstein. The site has an area of 620 hectares (1,500 acres) which consists of the mudflats on the tidal current of the river Eider. It is run by the German Nature and Biodiversity Conservation Union, NABU.