Hennstedt was an Amt Kirchspielslandgemeinde ("collective municipality") in the district Dithmarschen in Schleswig-Holstein, in northern Germany. Its administration was in the village Hennstedt. In January 2008, it was merged with the Ämter Lunden and Tellingstedt to form the Amt Eider.
It consisted of the following municipalities (with population in 2005):