Mary "Mother of the Church" is the Marian title that Pope Paul VI proclaimed at the end of the Second Vatican Council on November 21, 1964. By this solemn act of the supreme magisterium, the Pope wanted to affirm "the maternal role that the Virgin exercises towards the Christian people." He thus wished, as requested by the Council, to promote the "filial piety" of all members of the Church towards the Mother of Jesus, who was given to us as a mother when Jesus said to John on the cross: "Behold your mother."
A perfect disciple of Jesus and a living incarnation of the Beatitudes, Mary is for us "the perfect model of the disciple of the Lord: the disciple who builds up the earthly and temporal city while being a diligent pilgrim towards the heavenly and eternal city; the disciple who works for that justice which sets free the oppressed and for that charity which assists the needy; but above all, the disciple who is the active witness of that love which builds up Christ in people's hearts.” (Paul VI, Marialis cultus, No. 37).
In 1931, Pope Pius XI instituted the feast of "The Divine Maternity of Mary" in commemoration of the fifteenth centenary of the opening of the Council of Ephesus that declared Mary, Mother of God. Pope John XXIII chose the same date to open the Second Vatican Council in 1962, placing the Council under the protection of the Blessed Virgin.
In 1974, during a reorganization of the liturgical calendar of the universal Church, Pope Paul VI moved the feast of Mary's Maternity from October 11th to January 1st, under the title of "Mary, Mother of God," thus renewing with an ancient Roman tradition.
Mary brings us back, beyond all hierarchical or legal considerations, to the intimate and essential dimension of the Church, for she is our mother in the order of grace, of our relationship with Jesus, of faith, hope, and love.