Prussia was a historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg, and centered on the region of Prussia. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organised and effective army. Prussia, with its capital in Königsberg and from 1701 moved to Berlin, shaped the history of Germany. In 1871, German states united to create the German Empire under Prussian leadership. In November 1918, the monarchies were abolished and the nobility lost its political power during the German Revolution of 1918–19. The Kingdom of Prussia was thus abolished in favour of a republic—the Free State of Prussia, a state of Germany from 1918 until 1933. From 1933, Prussia lost its independence as a result of the Prussian coup, when the Nazi regime was successfully establishing its "Gleichschaltung" laws in pursuit of a unitary state. With the end of the Nazi regime, the division of Germany into allied-occupation zones and the separation of its territories east of the Oder–Neisse line, which were incorporated into Poland and the Soviet Union, the State of Prussia ceased to exist de facto in 1945. Prussia existed de jure until its formal liquidation by the Allied Control Council Enactment No. 46 of 25 February 1947.

The name Prussia derives from the Old Prussians. In the 13th century, the Teutonic Knights—an organized Catholic medieval military order of German crusaders—conquered the lands inhabited by them. In 1308, the Teutonic Knights conquered the formerly Polish region of Pomerelia with Gdańsk (Danzig). Their monastic state was mostly Germanised through immigration from central and western Germany and in the south, it was Polonised by settlers from Masovia. The Second Peace of Thorn (1466) split Prussia into the western Royal Prussia, a province of Poland, and the eastern part, from 1525 called the Duchy of Prussia, a fief of the Crown of Poland up to 1657. The union of Brandenburg and the Duchy of Prussia in 1618 led to the proclamation of the Kingdom of Prussia in 1701.