Coetus Internationalis Patrum

The Coetus Internationalis Patrum (Latin for International Group of Fathers) was a study group of the conservative-minded bishops at the Second Vatican Council. The members included prelates such as Cardinals Francis Spellman, Alfredo Ottaviani, Archbishop Marcel Lefebvre, and Bishops Casimiro Morcillo of Madrid, Antônio de Castro Mayer of Campos and Geraldo de Proença Sigaud of Diamantina.

It was originally formed after complaints by some of the more traditionalist bishops of the presence of Protestants and liberal Catholic theologians such as Hans Küng, Joseph Ratzinger (the future Pope Benedict XVI) and Karl Rahner.

As a member of the Preparatory Commission for the Second Vatican Council, Archbishop Marcel Lefebvre took part in the discussions about the draft documents submitted to the bishops for consideration at the Council. During the first session of the Council (October to December 1962), he became concerned about the direction the Council's deliberations were taking. Together with several other like-minded bishops, including Bishop Antônio de Castro Mayer, Lefebvre established a study group of bishops at the Council which organized lectures by important theologians. Eventually this group became known as the Coetus Internationalis Patrum.

This study group was concerned about a number of issues at the Council. They feared that episcopal collegiality could undermine papal primacy. They thought there should be a specific condemnation of communism. They thought there should be a specific Council document about the Blessed Virgin Mary, not merely a chapter in Lumen gentium. Some also favoured a solemn definition of a fifth Mariological dogma, which would proclaim Mary as Co-Redemptrix, Mediatrix and advocate for the Church with the Most Blessed Trinity.

Continuing complaints from the group about the presence of Protestant observers led Pope Paul VI, who was "concerned not to alienate the traditionalists", to ask Cardinal Augustin Bea "if perhaps the presence of the 'separated brethren' and their 'mentality' were 'excessively dominating the council, thus diminishing its psychological freedom.' (He) emphasized that protecting 'the coherence of the teaching of the Catholic Church' was more important than pleasing the observers.'" After thus consulting Cardinal Bea, the Pope decided not to disinvite the observers.