East Prussia, the eastern part of the region of Prussia West Prussia, the western part of the region of Prussia Province of West Prussia, a province of the Kingdom of Prussia, annexed from Poland in 1772 (former Royal Prussia), re-established 1878 Province of East Prussia, a province of the Kingdom of Prussia, created from former Ducal Prussia and Warmia in 1773, re-established 1878; an exclave of Germany after World War I Posen-West Prussia, a province of the Free State of Prussia (1922–1938) (the western parts of former West Prussia that were retained by Germany) Regierungsbezirk West Prussia, administrative region of the Province of East Prussia (1920–1938) (the eastern parts of former West Prussia that were retained by Germany)