Treaty of Pozvol

The Treaty or Peace of Pozvol, Pasvalys or Pozwol was a peace treaty and an alliance concluded on 5 and 14 September 1557 between the Livonian Confederation and the Polish-Lithuanian union, whereby the former put its territories under Polish-Lithuanian protection. The treaty was preceded by disputes between the members of the Livonian Confederation and military pressure by Sigismund II Augustus, king of Poland and Grand duke of Lithuania, and provoked Russian tsar Ivan IV "the Terrible" to start the Livonian War.

Albert (Albrecht), Grand Master of the Teutonic Knights, had introduced the Protestant Reformation and secularized the southern part of the Teutonic Order State, creating Europe's first Protestant state in the Duchy of Prussia in 1525 under Polish protection. His efforts to introduce Protestantism to the order's Livonian territories met with resistance and divided the Livonian Confederation.

When Albert's brother Wilhelm, who as Archbishop of Riga attempted to implement a Lutheran church order in his bishopric, appointed Protestant Christopher, Duke of Mecklenburg as his bishop coadjutor, the Catholic estates rebelled and arrested both Wilhelm and Christopher.