The Prussian Confederation (German: Preuischer Bund, Polish: Zwizek Pruski) was an organization formed on 21 February 1440 at Kwidzyn (then officially Marienwerder) by a group of 53 nobles and clergy and 19 cities in Prussia, to oppose the arbitrariness of the Teutonic Knights. It was based on an earlier similar organization, the Lizard Union established in 1397 by the nobles of Chemno Land.

In 1454, the leader of the Confederation, Johannes von Baysen (Jan Bayski), formally asked King Casimir IV Jagiellon, to incorporate Prussia into the Kingdom of Poland. This marked the beginning of the Thirteen Years' War between the Order's State and Poland, with the cities co-financing the military costs of the latter.

The Thirteen Years' War (German: Dreizehnjähriger Krieg; Polish: wojna trzynastoletnia), also called the War of the Cities, was a conflict fought in 1454–1466 between the Prussian Confederation, allied with the Crown of the Kingdom of Poland, and the State of the Teutonic Order.

The war began as an uprising by Prussian cities and local nobility to win independence from the Teutonic Knights. In 1454 Casimir IV married Elisabeth of Habsburg and the Prussian Confederation asked Poland's King Casimir IV Jagiellon for help and offered to accept the king as protector instead of the Teutonic Order. When the King assented, war broke out between supporters of the Prussian Confederation, backed by Poland, and backers of government by the Teutonic Knights.

The Thirteen Years' War ended in the victory of the Prussian Confederation and Poland and in the Second Peace of Thorn (1466). This was soon followed by the War of the Priests (1467–1479), a drawn-out dispute over the independence of the Prussian Prince-Bishopric of Warmia (Ermland), in which the Knights also sought revision of the Peace of Thorn.