St. Agnes was born in Prague in the year 1200, and probably died in the year 1281. She was the daughter of Ottocar, King of Bohemia and Constance of Hungary, who was a relative of St. Elizabeth. At an early age she was sent to the monastery of Treinitz, where she was educated in the hands of the Cistercian religious, who would eventually become her rank.
She was betrothed to Frederick II, Emperor of Germany, but when the time arrived for the solemnization of the marriage, it was impossible to persuade her to abandon the resolution she had made of consecrating herself to the service of God in the sanctuary of the cloister.
The Emperor Frederick was incensed at the unsuccessful issue of his matrimonial venture, but, on learning that St. Agnes had left him to become the spouse of Christ, he is said to have remarked: "If she had left me for a mortal man, I would have taken vengeance with the sword, but I cannot take offence because in preference to me she has chosen the King of Heaven."
The servant of God entered the Order of St. Clare in the monastery of St. Saviour at Prague, which she herself had erected. She was elected abbess of the monastery, and through this office became a model of Christian virtue and religious observance for all. God favoured her with the gift of miracles, and she predicted the victory of her brother Wenceslaus over the Duke of Austria.
The exact year of Agnes' death is not certain, but 1281 is the most probable date. She was beatified in 1874 by Pope Pius IX and canonized by Pope John Paul II on November 12, 1989.