The Immaculate Conception is the Catholic dogma that the Blessed Virgin Mary was conceived without original sin from the very first moment of her existence. This is NOT about the conception of Jesus — a common misconception. It means Mary herself was preserved from original sin by a special grace from God, in anticipation of her role as the Mother of God. This dogma was formally defined by Pope Pius IX in 1854 in the bull Ineffabilis Deus. It was confirmed by Mary herself at Lourdes in 1858 when she told St. Bernadette, 'I am the Immaculate Conception.' The Feast of the Immaculate Conception is celebrated on December 8 and is a Holy Day of Obligation in the United States.