Alfrink, Jan Bernard (1900–1987), Cardinal-Archbishop of Utrecht. Member of the Central Preparatory Commission and member of the Council of Presidents.

Stephen F. Bayne (1908–1974), American Episcopalian and Bishop of the Diocese of Olympia, 1946–1959. In 1959 he was appointed the first Executive Officer of the Anglican Communion by the Archbishop of Canterbury. He was also made Bishop-in-Charge of the Episcopal Church's Convocation of American Churches in Europe.

Bea, Augustin (1881–1968), German Jesuit and former Rector of the Pontifical Biblical Institute (1930–1949). Member of the Central Preparatory Commission and in 1960 made President of the newly established Secretariat for Christian Unity. His interest in ecumenical matters was long-standing and he was held in high esteem by many of the observers.

Browne, Michael (1887–1971), Cardinal. Irish Dominican. Rector of the Angelicum (1932–1941) and Master General of the Dominicans (1955–1962). Member of the Preparatory Commission on Bishops and Vice-President of the Doctrinal Commission.

Butler, Christopher (1902–1986), English convert to Roman Catholicism and the seventh Abbot of Downside Abbey, home to Benedictine monks. He was present for all four sessions of the Council and was a member of its Commission for Doctrine. Butler also participated in the debate on war and peace, with particular reference to nuclear deterrence.

Cardinale, Igino Eugenio (1916–1983), Apostolic Delegate to Great Britain, 1963–1969.

Cicognani, Amleto Giovanni (1883–1973), Italian Cardinal. Secretary of State, 1961–1969. Prefect of the Congregation for the Oriental Churches and member of the Central Preparatory Commission. President of the Preparatory Commission on the Oriental Churches, President of the Council's Commission on the Oriental Churches, and President of the Coordinating Commission.

Congar, Yves-Marie (1904–1995), French Dominican and Professor of Theology at Le Saulchoir. He was consultant for the Preparatory Commission and served as peritus on several commissions. In 1950 he was censured after the encyclical Humanis Generis but was made a cardinal in 1994. His journal from the Council has recently been published in an English translation.

Cullmann, Oscar (1902–1999), German Lutheran theologian. Professor of New Testament Studies at Basel, Paris, and the Sorbonne. He was Pope John XXIII's personal guest at the Council. After the Council closed he co-founded the Ecumenical Institute of Tantur in Jerusalem.

De Smedt, Émile-Joseph (1909–1995), Bishop of Bruges. Vice-President of the Secretariat for Christian Unity and an important spokesman in the Council for the Secretariat. He presented the early draft supporting religious liberty to the Council.

Döpfner, Julius (1913–1976), Cardinal-Archbishop of Munich. Member of the Central Preparatory Commission and of the Coordinating Commission. One of the moderators at the Council.

Fisher, Geoffrey Francis (1887–1972), ordained an Anglican priest in 1913. In 1939 he was made Bishop of London and in 1945 he became Archbishop of Canterbury, a post that he retained until 1961. His visit to Pope John XXIII in December 1960 profoundly changed the relations between the Church of England and Rome.

Frings, Joseph (1887–1978), Archbishop of Cologne from 1942. Member of the Central Preparatory Commission and a member of the Council of Presidents. During the Council Joseph Ratzinger was his personal advisor.

Heenan, John (1905–1975), Archbishop of Westminster from 1963 until his death. Elevated to the Cardinalate in 1965. During the Council he famously launched an attack on the periti as he felt that they were undermining the faith (‘timeo peritos et dona ferentes’: ‘I fear experts and those bearing gifts’). But even before the Council opened he had been appointed to the newly established Secretariat for Christian Unity.

John XXIII, Angelo Giuseppe Roncalli (1881–1963). In 1921 he was called to Rome to reorganize the Society for the Propagation of the Faith. Upon being nominated Titular Archbishop of Areopolis and Apostolic Visitor to Bulgaria (1925), he focused on the problems of the Eastern churches. In 1953 he became Cardinal-Patriarch of Venice, and expected to spend his last years there doing pastoral work. His election to Pope in 1958 came as a surprise to both himself and onlookers. Less than three months into his pontificate he announced that he would convoke an ecumenical council for the universal Church.

König, Franz (1905–2004), Cardinal-Archbishop of Vienna and a member of the Central Preparatory Commission. In 1962 he was elected to the Doctrinal Commission and was a wholehearted supporter of Nostra Aetate. He was convinced that the Roman Church should seek closer relations with the Orthodox churches and should take a clear stand against anti-Semitism. He named Karl Rahner his personal theologian for the Council.

Lefebvre, Marcel (1905–1991), missionary in Africa and Archbishop of Dakar (Senegal). In 1962 he was elected superior-general of the Holy Ghost Fathers and became a member of the Central Preparatory Commission. He was concerned about the direction that the Council was taking and became a member of the group of bishops known as Coetus Internationalis Patrum. He repudiated the Council and was excommunicated in 1988 for ordaining four bishops for his schismatic group – without papal approval. In 2009 Pope Benedict XVI lifted the excommunication of the four bishops, a move which caused much controversy.

Léger, Paul-Émile (1901–1994), Cardinal-Archbishop of Montreal and a member of the Preparatory Commission, the Doctrinal Commission, and the Commission on Canon Law.

Lercaro, Giacomo (1891–1976), Cardinal-Archbishop of Bologna. After the death of John XXIII he was regarded as papabile and was a member of the Liturgical Commission. Lercaro was active in the ‘Church of the Poor Group’.

Liénart, Achille (1884–1973), Cardinal-Archbishop of Lille and President of the French Episcopal Conference. He was a member of the Central Preparatory Commission, sat on the Council of Presidents, and was also a member of the Coordinating Commission.

Maximos IV Saigh (1878–1967), Melchite Patriarch of Antioch (Syria) and leader of the Melchite bishops at the Council. He was a member of the Central Preparatory Commission and of the Commission on the Oriental Churches. Although the official language of the Council was Latin, Saigh was notorious for slipping into French most of the time. At the Council he advocated the use of vernacular languages at services and championed Eastern orthodoxy.

Moorman, John (1905–1989), Anglican clergyman and Bishop of Ripon (1959–1975). Archbishop Michael Ramsey appointed him chief Anglican Observer at the Second Vatican Council from 1962 to 1965. Moormann was fluent in Italian and enjoyed a personal friendship with Cardinal Montini (who was to become Pope in 1963). In 1967 he became the Anglican chairman of the Preparatory Commission which led to the setting up of the Anglican–Roman Catholic International Commission, of which he was a member from 1969 until 1981. He was also the driving force behind establishing the Anglican Centre in Rome.

Ottaviani, Alfredo (1890–1979), Italian cardinal and Secretary (head) of the Holy Office from 1959. Member of the Central Preparatory Commission and President of the Preparatory Theological Commission and of the Doctrinal Commission. Before and during the Vatican II years he resisted the development of doctrine which led the Council to approve the Declaration on Religious Freedom.

Paul VI, Giovanni Battista Enrico Antonio Maria Montini (1897–1978), Cardinal-Archbishop of Milan. He was appointed to the Central Preparatory Commission for the Second Vatican Council and also to the Technical-Organizational Commission. Upon his election as Pope in June 1963 he committed himself, in his first message to the world, to continue the work begun by his predecessor.

Pawley, Bernard Clinton (1911–1981), Anglican clergyman. Canon Residentiary of Ely Cathedral and from 1972 Archdeacon of Canterbury Cathedral. He was chosen by the Archbishop of Canterbury for the Anglican liaison in Rome as he spoke Italian and had many contacts with Christians in Germany, Belgium, Italy, and France.

Ramsey, (Arthur) Michael (1904–1988), ordained an Anglican priest in 1929. He served in parish and academic appointments until 1952, when he was appointed Bishop of Durham. He then served as Archbishop of York from 1956 until 1961 and Archbishop of Canterbury from 1961 until 1974. As a keen ecumenist Ramsey was bitterly disappointed when the Synod would not endorse a scheme for Anglican–Methodist unity. He was the first Archbishop of Canterbury in modern times to visit the Vatican formally, when he was received in the Sistine Chapel by Paul VI in 1966.

Ruffini, Ernesto (1888–1967), Cardinal-Archbishop of Palermo and a member of the Central Preparatory Commission and of the Council of Presidents.

Schlink, Bernhard (1903–1984), leading ecumenical theologian who observed the entire Council as a delegate of the Evangelical Church in Germany.

Siri, Giuseppe (1906–1989), Cardinal-Archbishop of Genoa and a member of the Central Preparatory Commission and of the Council of Presidents. In 1959 he was appointed the first President of the Italian Episcopal Conference by Pope John XXIII, a post which he held until 1965.

Skydsgaard, Kristen Ejner (1902–1990), Danish Lutheran theologian and Professor of Dogmatic Theology at the University of Copenhagen (1942–1972). On behalf of the Lutheran Council of Churches he was present at Vatican II as an Observer and contributed prolifically to the dialogue between the Catholic Church and the Lutheran churches.

Spellman, Francis (1889–1967), Cardinal-Archbishop of New York. He was the first American assistant to the Papal Secretariat of State (1925–1931). During the Council he was a member of the Central Preparatory Commission, of the Council of Presidents, and of the Coordinating Commission. Spellman lobbied for restored diplomatic relations between the United States and the Vatican and later supported American involvement in Vietnam.

Suenens, Léon-Joseph (1904–1996), Cardinal-Archbishop of Malines-Brussels and a member of the Central Preparatory Commission and of the Coordinating Commission. He recommended to Pope John XXIII that the Council should focus on a handful of key questions and should divide the work into internal church reform on the one hand and the Church's relations with the rest of the world on the other. In June 1963, Pope Paul VI made Suenens one of the four moderators of the Council who presided over it. He was in favour of the Church re-examining its condemnation of contraception and when Pope Paul took the question out of the hands of the Council Suenens warned of ‘another Galileo case’.

Tardini, Domenico (1988–1961), named Secretary of State by the newly elected Pope John XXIII in 1958. Famously a conservative at the Council.

Tisserant, Eugène (1884–1972), French cardinal and Dean of the Sacred College of Cardinals. He was a member of the Central Preparatory Commission and then of the Doctrinal Commission.

Willebrands, Johannes (1909–2006), Dutch priest and later bishop and cardinal, whose frequent travelling to ecumenical gatherings earned him the name of ‘the flying Dutchman’. In 1948 he founded the Catholic Conference on Ecumenical Questions; although it did not seek the Holy See's approval it kept the latter informed of its activities. The Conference was in informal contact with the World Council of Churches. Until he was made titular bishop in 1964, Willebrands was Council peritus. On the penultimate day of the Council it was he who read out the momentous declaration cancelling the mutual excommunication of the Catholic and Orthodox churches in 1054. Upon the death of Cardinal Bea in 1968 Willebrands succeeded him as President of the Secretariat for Christian Unity.