Heir to two crowns, he refused a throne offered by force of arms and died at twenty-five.
Second son of king Casimir IV Jagiellon, born at Kraków in 1458, he was tutored by the historian Jan Długosz. At thirteen a faction of Hungarian nobles offered his father the crown of Hungary against Matthias Corvinus; the army sent in his name broke up for lack of pay, and Casimir afterwards refused to resume the enterprise, judging the war unjust — an attitude that earned him his father's displeasure and confinement at Dobzki castle. Recalled to court, he administered Poland during his father's absences in 1481 and 1483 and was noted for his justice towards the peasantry. He refused the marriage proposed to him with a daughter of the emperor, having vowed chastity. Tubercular, he died in 1484 at Grodno, aged twenty-five. Canonised in 1602, he is patron of Poland and Lithuania, and is commemorated on 4 March.
Shown as a young prince, crown and lily in hand, sometimes with three hands — a painter's error taken up by tradition.