The Immaculate Conception, according to the teaching of the Catholic Church, was the conception of the Blessed Virgin Mary in her mother’s womb free from original sin by virtue of the foreseen merits of her son Jesus Christ.
The Immaculate Conception is commonly confused with the doctrine of the Incarnation and the virgin birth of Jesus, though the two deal with separate subjects. The Catholic Church teaches that Mary was conceived by normal biological means, but God acted upon her soul (keeping her “immaculate”) at the time of her conception.
Although the belief that Mary was sinless and conceived immaculate has been widely held since Late Antiquity, the doctrine was not dogmatically defined until 1854, by Pope Pius IX in his papal bull Ineffabilis Deus. The Catholic Church celebrates the Feast of the Immaculate Conception on December 8; in many Catholic countries, it is a holy day of obligation or patronal feast, and in some a national public holiday.