• Duchy of Prussia 1525–1701 was a duchy in the region of Prussia established as a result of secularization of the State of the Teutonic Order during the Protestant Reformation in 1525.
• Brandenburg-Prussia 1618–1701
• Kingdom of Prussia 1701–1918

Started on the shore of the Baltic Sea then merged with Brandenburg in Germany (through marriage), then became associated with Germany as Kingdom of Prussia.

Nowadays, that part of Germany is back to being called Brandenburg.

Prussia (region) stretching from Gdańsk Bay to the end of Curonian Spit on the southeastern coast of the Baltic Sea, and extending inland as far as Masuria.

The territory and inhabitants were described by Tacitus in Germania in AD 98, where Suebi, Goths and other Germanic people lived on both sides of the Vistula River, adjacent to the Aesti (further east).

About 800 to 900 years later the Aesti were named Old Prussians, who, since 997, repeatedly defended themselves against take-over attempts by the newly created Duchy of the Polans. The territory of the Old Prussians and neighboring Curonians and Livonians was unified politically in the 1230s as the State of the Teutonic Order.

Prussia was politically divided between 1466 and 1772, with western Prussia under protection of the Crown of Poland and eastern Prussia a Polish–Lithuanian fief until 1660. The unity of both parts of Prussia remained preserved by retaining its borders, citizenship and autonomy until western and eastern Prussia were also politically reunited under the German Kingdom of Prussia (which despite the name was based in Berlin, Brandenburg).