The Province of West Prussia (German: Provinz Westpreußen; Kashubian: Zôpadné Prësë; Polish: Prusy Zachodnie) was a province of the Kingdom of Prussia from 1773–1824 and from 1878–1919/20, within the German Reich, which was created out of the earlier Polish province of Royal Prussia. In February 1920, Germany (after it had been defeated in 1918) handed over West Prussia's mainly German populated central parts to become the so-called Polish Corridor (i.e. Pomeranian Voivodeship) and the Free City of Danzig, while the parts remaining with the German Weimar Republic became the new Posen-West Prussia or were joined to the Province of East Prussia as Regierungsbezirk West Prussia. The territory was included within Reichsgau Danzig-West Prussia from 1939–45, after which it became part of Poland.

West Prussia is also used as a general name for the region in historical context from the 13th century to 1945.

In the Middle Ages, it was inhabited by Slavic and Baltic tribes: by Pomeranians in Pomerelia west to Vistula river, by Old Prussians and later Masovians in Kulmerland, and by Old Prussians (mainly Pomesanians) in the part of the region located east to Vistula river and north to Kulmerland. Due to immigration and cultural changes, the population became mixed over centuries and consisted of Germans, Kashubians, Poles, as well as Slovincians, Huguenots, Mennonites, and Jews, among others.

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).

History

Most of Polish Royal Prussia was annexed by King Frederick the Great of Prussia in the 1772 First Partition of Poland. The town of Marienwerder, previously in Ducal Prussia, became an administrative capital of the newly acquired territory, which became the Province of West Prussia on 31 January 1773.