Catholic Encyclopedia (1913)/Zbigniew Olesnicki
A Polish cardinal and statesman, b. in Poland, 1389; d. at Sandomir, 1 April, 1455. At the age of twenty he was secretary to King Jagello, and fought with him in the battle of Grünwald on 14 July, 1410. A favourite with the king, he took part in the management of the country's most important affairs. His influence with the king greatly aided him in opposing the Hussites, who had gained royal favour. On 9 July, 1423, he was appointed to the episcopal see of Cracow, and in 1433 he was sent by the king as legate to the council of Basle, where he endeavoured to be on friendly terms with both parties. On 18 December, 1439, he was created cardinal priest with the titular church of St. Prisca, by Eugene IV. The opinion that he accepted the same dignity from the antipope Felix V and adhered to him for some time has recently been attacked by P.M. Baumgarten: "Die beiden ersten Kardinals Konsistorien des Gegenpapstes Felix V" in "Römische Quartalschrift", XXII (Rome, 1908), 153. As cardinal, his influence in Poland was second only to that of the king, and, during the frequent absence of Casimir IV in Lithuania, he transacted the affairs of the State. Being a man of great learning, he advanced the study of arts and letters in every possible way, and the flourishing condition of the University of Cracow during his episcopacy is due chiefly to his efforts. To repress the spread of Hussitism he called John Capistran and the Minorites to Cracow.
Cardella, Memorie storiche de'cardinali della s. romana chiesa, III (Rome, 1792), 81-4; Dzieduszycki, Zbigniew Olesnicki (2 vols., Cracow, 1853-4), in Polish; Zegarski, Polen u. das Basler Konzil (Posen, 1910).