Born Dec. 5, 1389, in Sienno; died Apr. 1, 1455, in Sandomierz. Polish church leader. Bishop of Kraków from 1423 and cardinal from 1449.
Oleśnicki headed the Catholic magnate faction in Poland and dominated Polish politics from the 1420’s to the 1440’s. He combatted all manifestations of Hussitism in Poland and opposed the projected union between Poland and Hussite Bohemia. At the same time, he supported closer ties between Poland and Lithuania and promoted the Polish-Hungarian union of 1440. Advocating eastward expansion and the annexation of Volyn’ and Podolia, Oleśnicki did not support Poland’s struggle against the Teutonic Order.