The Prussian Confederation (German: Preußischer Bund, Polish: Związek 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 Chełmno Land.

In 1454, the leader of the Confederation, Johannes von Baysen (Jan Bażyński), 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.