Posen–West Prussia

The Frontier March of Posen–West Prussia (German: Grenzmark Posen-Westpreußen; Polish: Marchia Graniczna Poznańsko-Zachodniopruska) was a province of Prussia that existed from 1920 (de facto) and 1922 (de jure) until its dissolution in 1938. It comprised most of the former territory of West Prussia and parts of the Province of Posen that had remained within Germany following the territorial losses to the Second Polish Republic after the Greater Poland Uprising, and confirmed by the Treaty of Versailles. The province was created in 1922 as part of the Free State of Prussia within Weimar Germany, incorporating three remaining non-contiguous territories of the former provinces of Posen and West Prussia.

Schneidemühl (present-day Piła) served as the provincial capital. From 1934 onwards, the province came under the de facto administration of the Province of Brandenburg, and on 1 October 1938, the territory was officially dissolved by Nazi Germany. Its lands were subsequently incorporated into the neighbouring provinces of Pomerania, Brandenburg and Silesia. Following the end of World War II and the redrawing of borders, the entire area of the former province was incorporated into Poland, lying east of the Oder–Neisse line.