Old Prussia may refer to different entities, which were also territorially defined.
In political and territorial respect it refers to:
- Old Prussia
- The Provinces of Prussia officially formed in 1815 or partially later, whose territories belonged to the Kingdom of Prussia before 1815 or before 1866, especially:
- in a narrow sense the expression means the entirety of the:
- Province of Brandenburg
- Province of East Prussia
- Province of Pomerania
- Province of Prussia, combining East and West Prussia between 1829 and 1878
- Province of Silesia
- Province of West Prussia
- in the broad sense of the expression the following provinces are also included:
- in a narrow sense the expression means the entirety of the:
In religious and territorial respect it refers to:
- Evangelical State Church of Prussia's older Provinces, renamed into Evangelical Church of the old-Prussian Union (1922–1953).
Source: Der Große Brockhaus: Handbuch des Wissens in zwanzig Bänden: 21 vols., 15th totally revised ed., Leipzig: F. A. Brockhaus, 1928–1935, vol. 1: A–Ast, article: 'Altpreußen', p. 356. No ISBN.