Councils
The 21 ecumenical councils recognized in Catholic tradition, from Nicaea (325) to Vatican II (1962–1965). Other Christian communions receive different sets of councils.
Each page explains its context and teaching. Available in-app source texts are linked directly; external editions and incomplete text coverage are labeled. A council’s doctrinal teaching and historical disciplinary rules must be distinguished.
First Council of Nicaea
325
The relation of the Son to the Father during the Arian controversy.
First Council of Constantinople
381
Trinitarian disputes, especially the divinity of the Holy Spirit.
Council of Ephesus
431
Disputes about the unity of Christ and the title Theotokos.
Council of Chalcedon
451
How to confess Christ’s full divinity and full humanity without division or confusion.
Second Council of Constantinople
553
The Three Chapters controversy and the interpretation of earlier Christological teaching.
Third Council of Constantinople
680–681
Monothelitism: the question of Christ’s divine and human wills and operations.
Second Council of Nicaea
787
Iconoclasm and the place of sacred images in Christian worship.
Fourth Council of Constantinople
869–870
The conflict involving Photius, Ignatius, episcopal appointments and ecclesial communion.
First Lateran Council
1123
Church reform and the settlement of the investiture controversy.
Second Lateran Council
1139
Healing the recent papal schism and continuing ecclesiastical reform.
Third Lateran Council
1179
The aftermath of papal schism, election procedure and reform.
Fourth Lateran Council
1215
Doctrinal clarification, pastoral reform and the ordering of medieval Christian life.
First Council of Lyon
1245
The conflict between Innocent IV and Emperor Frederick II, alongside Church reform.
Second Council of Lyon
1274
East-West reunion, papal election arrangements and reform.
Council of Vienne
1311–1312
The Templar controversy, reform and questions of doctrine and religious life.
Council of Constance
1414–1418
The Western Schism, reform and controversies involving Wycliffe and Hus.
Council of Basel–Ferrara–Florence
1431–1445
Church reform, conciliar authority and attempts at reunion with Eastern Christians.
Fifth Lateran Council
1512–1517
Church reform, a rival assembly at Pisa and questions of faith and philosophy.
Council of Trent
1545–1563
Reformation controversies over Scripture, justification, the sacraments and Church reform.
First Vatican Council
1869–1870
Faith and reason, revelation, and the primacy and infallibility of the Roman pontiff.
Second Vatican Council
1962–1965
The Church’s life, worship, mission and relations with the modern world and other Christians.