Royal Prussia is a region (part of province of Greater Poland) of the Polish-Lithuanian Commonwealth that is carved out of the State of the Teutonic Order.

It consists of the following districts: Pomerelia (Gdańsk Pomerania) with Danzig (Gdańsk), Chełmno Land ('Kulmerland) with Michałów Land (Michelauer land) and Toruń (Thorn), the mouth of the Vistula with Elbląg (Elbing) and Malbork (Marienburg), the Bishopric of Warmia (Ermland) with Olsztyn (Allenstein ).

By the Second Peace of Thorn (1466), these districts are ceded to the Kingdom of Poland.

Until the 1569 Union of Lublin the region enjoys a substantial autonomy.

After 1569, Royal Prussia is directly administered by the Crown of the Kingdom of Poland in the Polish-Lithuanian Commonwealth.Administratively Royal Prussia becomes part of the Greater Poland Province together with Greater Poland proper, Masovia, and Łęczyca Voivodeship and Sieradz Voivodeship, with the Province capital being Poznań.