Dithmarschen (German: [ˈdɪtmaʁʃn̩] , Low Saxon: [ˈdɪtmaːʃn̩]; archaic English: Ditmarsh; Danish: Ditmarsken; Medieval Latin: Tedmarsgo) is a district in Schleswig-Holstein, Germany. It is bounded by (from the north and clockwise) the districts of Nordfriesland, Schleswig-Flensburg, Rendsburg-Eckernförde, and Steinburg, by the state of Lower Saxony (district of Stade, from which it is separated by the Elbe river), and by the North Sea.
From the 13th century up to 1559 Dithmarschen was an independent peasant republic within the Holy Roman Empire and a member of the Hanseatic League. It repulsed attempts by larger fiefs to annex it, whether physically (as with the invasions by Holstein in 1319 and 1404 or Denmark in 1500) or legally (as with their successful court battle against Holstein in 1474-1481). Dithmarschen was recognized as an imperial fief by the emperor, who summoned the peasants to send representatives to royal assemblies and the Imperial Diet. Its heyday was from the consolidation of its government in 1447 to its final conquest by the King of Denmark in 1559, though the Danish were still compelled to leave Dithmarschen with a considerable degree of autonomy.