Saint Casmir (also known as Kazimierz or Casimir) was a Polish prince and patron saint of Poland and Lithuania. He was born on October 3, 1458 and died on March 4, 1484.
Casmir was the son of King Casimir IV of Poland and Elisabeth of Austria. He was the third child and second son of the king. Despite his royal birth, Casmir lived a simple and ascetic life, dedicating himself to prayer and good works. He was known for his generosity to the poor and his devotion to the Christian faith.
One of Casmir's most significant accomplishments was his role in the Union of Krewo, a political agreement between Poland and Lithuania that united the two countries under a single ruler. He was also known for his efforts to promote peace and unity among the various factions within Poland and Lithuania.
Casmir's feast day is celebrated on March 4th, and he is the patron saint of Poland and Lithuania, as well as of bachelors, students, and youth. He is also invoked against kidney disease, gout, and rheumatism.
Casmir was also known for his devotion to the Virgin Mary, and it is said that he had a deep devotion to the rosary. He is said to have worn a hair shirt, and spent long hours in prayer before the Blessed Sacrament.
Although Casmir died at the young age of 25, his devotion and holiness left a lasting impression on those around him, and he was quickly venerated as a saint. His cult spread rapidly throughout Poland and Lithuania and eventually, the Catholic Church canonized him in 1522.