The Brandenburg-Prussian state was formed in 1618 when the Duchy of Prussia came under the control of the Elector of Brandenburg (part of the Holy Roman Empire of German Nation). Brandenburg-Prussia was succeeded by the Kingdom of Prussia in 1701 and the state was absorbed by the newly founded German Empire in 1871.

Anna, daughter of Duke Albrecht Friedrich of Prussia (reigned 1568-1618), married Elector Johann Sigismund of Brandenburg, who was granted the right of succession to Ducal Prussia (then a Polish fief) on his father-in-law's death in 1618. From this time the Polish fief Prussia came under the reign of the Electors of Brandenburg. Ducal Prussia stayed a fief under the Polish crown till 1660.

During the reign of Georg Wilhelm (1619-1640), the Hohenzollern lands were repeatedly marched across by various armies in the Thirty Years War, spending much of the war occupied by Sweden. Taking advantage of the difficult position of Poland with Sweden in the Northern War, and their friendly position with Russia during a series of Russo-Polish wars, "The Great Elector" Friedrich Wilhelm (1640-1688) obtained a discharge of his vassal obligations and after the Tatar invasion of Poland in 1656-67, was finally given independent control of Prussia in 1660.

However, the rights of Polish crown still applied in case of Hohenzollern extinction. In 1701 his son, Friedrich III, proclaimed himself Friedrich I, King in Prussia, and all links to Poland were removed. The first Prussian King was also the last who spoke fluent Polish. His successors spoke fluent French and German. (see Kingdom of Prussia)