Gaudet Mater Ecclesia (Latin for "Mother Church Rejoices") is the opening declaration of the Second Vatican Council.
Pope John opened the Council on October 11, 1962, in a public session before the Council Fathers as well as representatives of 86 governments and international bodies. Following a Mass, the Pope read the opening declaration.
In the speech, he rejected the thoughts of "prophets of doom who are always forecasting disaster" in the world and in the future of the Church. Pope John stressed the pastoral, not doctrinal, nature of the Council: The Church did not need to repeat or reformulate existing doctrines and dogma but rather had to teach Christ's message in light of the modern world's ever-changing trends.
He exhorted the Council Fathers "to use the medicine of mercy rather than the weapons of severity" in the documents they would produce.
Gaudet Mater Ecclesia stated the purpose of the Second Vatican Council to be defending and presenting the sacred deposit of Christian doctrine:
The greatest concern of the Ecumenical Council is this, that the sacred deposit of Christian doctrine should be more effectively defended and presented.
The document previewed what Pope John Paul II would later call the New evangelization.