thumb|right|300px|Administrative regions of West Prussia:
Regierungsbezirk Marienwerder was a Regierungsbezirk (governorate), or administrative region, of Prussia from 1815 until 1945. Marienwerder region was part of the Province of West Prussia from 1815–1829, and again 1878–1920, belonging to the Province of Prussia in the intermittent years. Marienwerder region was then placed under an inter-allied commission from 1920–22. It was known as Regierungsbezirk Westpreußen ("West Prussia") while it was joined to the Province of East Prussia from 1922–39, after which its original name was restored until its dissolution in 1945. The regional capital was Marienwerder (Kwidzyn).
The German place name Marienwerder refers to:
- Marienwerder, the German name of the city Kwidzyn in Poland
- Marienwerder (region), a former government region of Prussia
- Marienwerder (district), a former district of Prussia
- Marienwerder, Brandenburg, a community in the administrative district of Barnim, Germany
- Part of the urban district Herrenhausen-Stöcken in the city of Hanover, Germany
Landkreis Marienwerder was a Kreis, or district, of Prussia from 1752-1945. Its capital was Marienwerder (Kwidzyn).