St. Casimir
A prince of Poland and Lithuania sent at thirteen to claim the Hungarian throne, who refused a dynastic marriage and died of tuberculosis at Grodno in 1484, aged twenty-five.
Canonized
St. Casimir (Catholic Encyclopedia)
Sources
- General Roman Calendar, 4 March — 'St Casimir'. Liturgy Office, England and Wales. https://www.liturgyoffice.org.uk/Calendar/Info/General-Roman-Calendar.pdf
- USCCB Liturgical Calendar 2026, 4 March — 'Saint Casimir' (optional memorial). https://www.usccb.org/resources/2026cal.pdf
- Catholic Encyclopedia (Herbermann, 1907-1913), 'St. Casimir' — born in the royal palace at Cracow, 3 October 1458, second son of King Casimir IV; at thirteen accepted the offer of the Hungarian crown from discontented nobles and 'returned a fugitive to Poland'; declined the marriage his father sought to arrange with a daughter of Emperor Frederick III; died at the court of Grodno, 4 March 1484, of lung trouble. https://www.newadvent.org/cathen/03402a.htm
- STATUS_YEAR IS NULL BECAUSE THE SOURCES CONFLICT THREE WAYS AND CANNOT BE ADJUDICATED. (1) Vatican City State's own saint-of-the-day page: 'He was canonized in 1521 by Pope Leo X.' (2) The Catholic Encyclopedia: an investigation ordered by Leo X was completed in 1520 and 'in 1522 Casimir was canonized by Adrian VI' — Leo X having died in December 1521. (3) The earliest act with surviving documentation is a brief of Clement VIII in 1602, with the ceremony following in 1604. The original canonization records are believed lost in the 1527 Sack of Rome. The canonization itself is not in doubt, so status_basis stays 'formal'; the year is not establishable, so it is omitted rather than shipped as the traditional guess. Do not 'fix' this to 1521.
- Note on the one_line: he did not refuse the Hungarian throne — he accepted it at thirteen and the expedition failed. What he refused was the dynastic marriage.