Marschacht is a municipality located in the district of Harburg within the state of Lower Saxony, Germany. It forms part of the Samtgemeinde Elbmarsch along with the neighboring municipalities of Tespe and Drage. The town is situated only a few kilometers away from Geesthacht.
The settlement was first documented in 1216 under the name Hachede and was originally part of Saxony. Historically, a change in the course of the Elbe river resulted in the settlement being divided into two distinct areas: Geesthacht and Marschacht.