Horst-Herzhorn is an Amt (collective municipality) in the district of Steinburg, in Schleswig-Holstein, Germany. The seat of the Amt is in Horst. Before 1 January 2008, when it was merged with the Amt Herzhorn, it was named Amt Horst. The Amt Horst-Herzhorn consists of the following municipalities: Altenmoor Blomesche Wildnis Borsfleth Engelbrechtsche Wildnis Herzhorn Hohenfelde Horst Kiebitzreihe Kollmar Krempdorf Neuendorf bei Elmshorn Sommerland Ämter in Schleswig-Holstein