Ossoliński, Jerzy, b 15 December 1595 in Sandomierz, Poland, d 9 August 1650 in Warsaw. Polish statesman and diplomat. After completing his studies in France and Italy, he was a court functionary, adviser to King Władysław IV Vasa, and vice-chancellor (1638) and chancellor (1643) of the Polish-Lithuanian Commonwealth. Throughout the 1640s he maintained a relationship with the Ukrainian statesman Adam Kysil, whom he provided with access to his inner circles of power while benefiting from his knowledge of Ukrainian affairs and status as an acceptable mediator in disputes. Ossoliński was involved in negotiations to establish a new (Uniate) church union, as well as a scheme to create a broad-based coalition against the Turks and Tatars, in which the Ukrainian Cossacks were to play a vital role. In May 1648 Ossoliński assumed effective interregnum control of the Commonwealth and became a key figure in determining the Polish strategy in the Cossack-Polish War. Although his efforts in obtaining a negotiated settlement initially failed, in the spring of 1649 he managed to sever the alliance between Hetman Bohdan Khmelnytsky and the Tatar khan Islam-Girei III and thus brought about the Treaty of Zboriv.
[This article originally appeared in the Encyclopedia of Ukraine, vol. 3 (1993).]