Mary, Mother of the Church – 01 June
The Blessed Virgin Mary has been given the title of Mother of the Church since she gave birth to Christ, the Head of the Church, and she became the Mother of the redeemed people before her Son had given up the spirit on the Cross. Pope Paul VI solemnly confirmed the title in an address to the Fathers of the Second Vatican Council on 21 November 1964 and decreed that the whole Christian people should, by the use of this beautiful title, give still greater honour to the Mother of God.
  ‘The joyous veneration given to the Mother of God by the contemporary Church, in light of reflection on the mystery of Christ and on his nature, cannot ignore the figure of a woman (cf. Gal 4:4), the Virgin Mary, who is both the Mother of Christ and Mother of the Church. In some ways this was already present in the mind of the Church from the premonitory words of Saint Augustine and Saint Leo the Great. In fact the former says that Mary is the mother of the members of Christ, because with charity she cooperated in the rebirth of the faithful into the Church, while the latter says that the birth of the Head is also the birth of the body, thus indicating that Mary is at once Mother of Christ, the Son of God, and mother of the members of his Mystical Body, which is the Church’ (Decree of the Sacred Congregation for Divine Worship).
(universalis.com)
From an allocution by Blessed Paul VI, Pope, at the Second Vatican Council
 The Blessed Virgin Mary, Mother of the Church Â
Meditating on the close relationships between Mary and the Church, for the glory of the Virgin Mary and for our own consolation, we proclaim the Most Blessed Mary Mother of the Church, that is to say of all the people of God, of the faithful as well as of the pastors, who call her the most loving Mother. And we wish that the Mother of God should be still more honoured and invoked by the entire Christian people by this most sweet title.
 Just as, in fact, the divine maternity is the basis for her special relationship with Christ, and for her presence in the economy of salvation brought about by Jesus Christ, thus it also constitutes the principal basis for the relations between Mary and the Church, since she is the mother of Him who, right from the time of His Incarnation in her virginal bosom, joined to Himself as head His Mystical Body which is the Church. Mary, then as mother of Christ, is mother also of all the faithful and of all the pastors.
This is a title, venerable brothers, not new to Christian piety; it is precisely by this title, in preference to all others, that the faithful and the Church address Mary. It truly is part of the genuine substance of devotion to Mary, finding its justification in the very dignity of the Mother of the word Incarnate.
  It is therefore with a soul full of trust and filial love that we raise our glance to her, despite our unworthiness and weakness. She, who has given us in Jesus the fountainhead of grace, will not fail to succour the Church, now flourishing through the abundance of the gifts of the Holy Ghost and setting herself with new zeal to the fulfilment of its mission of salvation.
  And our trust is even more lively and fully corroborated if we consider the very close links between this heavenly Mother of ours and mankind. Although adorned by God with the riches of admirable prerogatives, to make her a worthy Mother of the Word Incarnate, she is nevertheless very close to us. Daughter of Adam, like ourselves, and therefore our sister through ties of nature, she is, however, the creature who was preserved from original sin in view of the merits of the Saviour, and who possesses besides the privileges obtained the personal virtue of a total and exemplary faith, thus deserving the evangelical praise, beata quae credidisti (blessed art thou who believed). In her earthly life, she realised the perfect image of the disciple of Christ, reflected every virtue, and incarnated the evangelical beatitudes proclaimed by Christ. Therefore in her, the entire Church, in its incomparable variety of life and of work, attains the most authentic form of the perfect imitation of Christ.