The Immaculate Conception is a Catholic teaching that says Mary, the mother of Jesus, was conceived without original sin. It does not refer to the conception of Jesus, but to Mary’s own beginning in the womb of her mother. Catholics believe God granted her this special grace in anticipation of Jesus’ saving work. The doctrine was officially defined as dogma in 1854 by Pope Pius IX. It is called a “mystery” because it is understood as a truth of faith that goes beyond full human explanation.