The Treaty of Warsaw (Polish: Traktat warszawski, Swedish: Freden i Warszawa) was concluded on 18 November (O.S.) / 28 November 1705 during the Great Northern War.^[1] It was a peace treaty and an alliance between the Swedish Empire and the faction of the Polish–Lithuanian Commonwealth loyal to Stanisław Leszczyński.^[1][2]

Early in the Great Northern War, Charles XII of Sweden campaigned in the Polish–Lithuanian Commonwealth, where Augustus the Strong, Elector of Saxony, was king since 1697.^[3] Aimed at dethroning his adversary, Charles XII managed to have his candidate Stanisław Leszczyński elected king of Poland on 12 July 1704.^[3] Augustus' ally Peter the Great, tsar of Russia, was reluctant to engage Charles XII in a major battle as a consequence of the decisive defeat his army had suffered at Narva in 1700.^[3] A faction of the Polish and Lithuanian nobles did not accept Leszczyński's election,^[3] which had been imposed in neglect of the commonwealth's customs, and organized in the Sandomir or Sandomierz Confederation in support of Augustus.^[4] They declared the election illegal, outlawed Leszczyński's supporters who were organized in the Warsaw Confederation, declared war on Sweden and allied with Russia in the Treaty of Narva.^[5]

A Russo-Saxo-Polish-Lithuanian army was then assembled at Polotsk (Polatsk, Połock, Polockas),^[1][5] another allied army in Saxony,^[6] and a third allied force commanded by General Otto Arnold von Paykull (Pajkul) advanced towards Warsaw,^[1] where Charles XII and Leszczyński sojourned.^[5] Pajkul's Saxo-Polish-Lithuanian horse reached the outskirts of Warsaw on 31 July 1705, where they were defeated.^[7] The army at Polotsk was denied westward advance by Swedish forces under Adam Ludwig Lewenhaupt.^[1] Thus, Leszczyński was crowned king of Poland in Warsaw on 4 October 1705, and Sweden and the faction of the commonwealth represented by Leszczyński signed the treaty of Warsaw on 28 November.^[1]

Sweden was allowed to occupy the Polish–Lithuanian Commonwealth's towns and fortresses and recruit soldiers in its territory without restriction.^[1][2] Anti-Swedish alliances concluded by the commonwealth were declared void,^[2] Poland was to conclude treaties only with Charles XII's approval.^[1]

The commonwealth's regions Courland, Lithuania, Royal Prussia and Ruthenia were to export goods only through the Swedish port of Riga,^[2] the Polish port Połąga (Palanga, Palonga) in Courland was to be abandoned.^[1][2] In the territory of the commonwealth, Swedish merchants were granted substantial tax exemption and the right to settle and trade.^[1]

The treaty further divided the commonwealth's territories then under Russian occupation among the parties: The areas of Smolensk and Kiev were to be re-integrated into Poland–Lithuania, while Polish Livonia and Courland were to be ceded to Sweden upon their reconquest.^[2]

For future candidates to the Polish throne, the treaty was made part of the pacta conventa, meaning it had to be supported for any candidacy to become valid.^[1]

As intended, the treaty made an inner-Polish-Lithuanian reconciliation of the Warsaw and Sandomir confederations impossible.^[1] In early 1706, Augustus the Strong approached Warsaw with a cavalry force and ordered Johann Matthias von der Schulenburg to move the army assembled in Saxony into Poland–Lithuania.^[8] Schulenburg was intercepted and defeated by Carl Gustav Rehnskiöld in the Battle of Fraustadt.^[6][8] The army assembled in Polotsk had been moved to Grodno (Hrodna, Gardinas, Garten), where it was tactically defeated and forced to withdraw eastwards.^[6][8] Charles XII then occupied Saxony, forcing Augustus to abandon both the Polish crown and his allies in the Treaty of Altranstädt (1706).^[6][8]