prince of Poland. Born at Cracow he was the third son of Casimir IV, king of Poland. At the age of thirteen he was sent by his father to the Hungarian border with a large army, as the Hungarian nobles wished to have Casimir as their king in place of Matthias Corvinus. His own soldiers, however, deserted because their pay was in arrears and the Hungarian king had assembled an army to fight them. So Casimir went home, but was banished by his father to the castle of Dobzki. He also refused to take up arms again against any Christian country at a time when Christians were in great danger from the Turks, and refused to marry a daughter of Emperor Frederick III, preferring a life of celibacy, devotion, and austerity. This was one result of his early education by John Dlugosz, canon of Cracow. In 1481–3 he ruled over much of Poland with justice, prudence, and firmness. He died of tuberculosis at the age of twenty-six and was buried at Vilna. Miracles were soon reported at his tomb and he was canonized by Leo X in 1521. The hymn sometimes called St Casimir's, Ommi die dic Mariae, was not composed by him but by Bernard of Cluny in the 12th century; Casimir, however, frequently said it and a copy of it was buried with him. In the 16th to 17th centuries his supernatural help was claimed by the vast Grand-Duchy of Lithuania, whose patron he became, in conflicts against the Russians. Feast: 4 March.
AA.SS. Mar. I (1668), 837–57;B.L.S., iii. 37–8;Bibl. SS., iii. 859–906.
Subjects: Christianity — Medieval and Renaissance History (500 to 1500).