The Frontier March of Posen–West Prussia was a province of Prussia from 1922 to 1938, covering most of lands of historical Greater Poland that were not included in Second Polish Republic. Posen–West Prussia was established in 1922 as a province of the Free State of Prussia within Weimar Germany, formed from merging three remaining non-contiguous territories of Posen and West Prussia, which had lost the majority of their territory to the Second Polish Republic following the Greater Poland Uprising. From 1934, Posen–West Prussia was de facto ruled by Brandenburg until it was dissolved by Nazi Germany, effective 1 October 1938 and its territory divided between the provinces of Pomerania, Brandenburg and Silesia. Schneidemühl was the provincial capital. Today, lands of the province are entirely contained within Poland.

Greater Poland, often known by its Polish name Wielkopolska, is a Polish historical region of west-central Poland. Its chief and largest city is Poznań followed by Kalisz, the oldest city in Poland.