The Truce of Zamość was signed on November 20, 1648 during the siege of Zamość between the King of Poland John II Casimir of Poland and the Hetman of Zaporizhian Host Bohdan Khmelnytsky.
That truce ended the first raid of Bohdan Khmelnytsky army into the territory of modern Poland. During the siege of Zamość that started two weeks prior to the signing of the truce on November 6, 1648, Bohdan Khmelnytsky had established diplomatic relations with government circles of the Polish–Lithuanian Commonwealth. His aim was to use the elections of a new King of Poland for insurgents' purposes. For tactical reasons the Hetman supported the candidacy of John II Casimir of Poland, hoping that John Casimir would be more amenable to a peace favorable to Khmelnytsky, than others candidates to the Crown. The Hetman's hopes came true. After the election of King John II Casimir Vasa, a true was signed at Zamość (the siege of the city of Zamość was lifted on November 24, 1648).
In the negotiations with diplomatic mission from the Cossack's side there was the brother of Hetman Zakhary Khmelnytsky, while the Polish–Lithuanian Commonwealth was represented by a priest Andrzej Mokrski (former teacher of Bohdan Khmelnytsky), noblemen J. Smiarowski and S. Oldakowski.
In the future, it was planned to establish a lasting peace, for which to the residence of Hetman in the beginning of 1649 had come a "committee" of the Commonwealth headed by Adam Kisiel.
The truce was a compromise. It had supporters and opponents on both the Ukrainian as well as the Polish side. Having concluded an armistice, Khmelnytskyi avoided the need to continue the campaign in late autumn during an epidemic that erupted in the Cossack army, which could have resulted in dire consequences for the insurgents. However, by signing the truce, the Hetman was forced to withdraw Cossack troops from most of the western-Ukrainian cities and partially from Podillia (Podolia). The truce of Zamość was short-lived, the Commonwealth first grossly violated it (the punitive offensive forces of the Grand Duchy of Lithuania into the Southern Belarus in January–February 1649). Another truce was signed later in Pereiaslav).