The immaculate conception is the conception of the Blessed Virgin Mary, free from original sin by virtue of the merits of her son Jesus Christ.
According to the Catholic Church, God acted upon Mary in the first moment of her conception, keeping her “immaculate”.
The event is commonly confused with the Virgin Birth of Jesus. Jesus’s birth is covered by the Doctrine of Incarnation. While the Immaculate Conception deals with the conception of Mary, not that of her son.
The doctrine of Immaculate Conception was not dogmatically defined until 1854 by Pope Pius IX in his papal Ineffabilis Deus.
In her honor, the Catholic Church celebrates the Feast of the Immaculate Conception on December 8.