(381), the second ecumenical council of the Christian church, summoned by the emperor Theodosius I and meeting in Constantinople. Doctrinally, it promulgated what became known to the church as the Nicene Creed; (Nicene Creed) it also declared finally the Trinitarian doctrine of the equality of the Holy Spirit with the Father and the Son. Among the council's canons was one giving the bishop of Constantinople precedence of honour over all other bishops except the bishop of Rome, “because Constantinople is the New Rome.”

Though only eastern bishops had been summoned (about 150 in all), the Greeks claimed this council to be ecumenical. Pope Damasus I in Rome appears to have accepted the creed but not the canons, at least not the canon upon the precedence of Constantinople. (Rome indeed accepted the precedence of Constantinople, next to Rome, only during the life of the Latin Empire of Constantinople, created in the 13th century during the Fourth Crusade.) In both East and West, nevertheless, the council came to be regarded as ecumenical.

(553), the fifth ecumenical council of the Christian church, meeting under the presidency of Eutychius, patriarch of Constantinople. Pope Vigilius of Rome, who had been summoned to Constantinople, opposed the council and took sanctuary in a church from May to December, but he at last yielded and formally ratified the verdicts of the council on Feb. 23, 554.

The 14 anathemas issued by the council rejected Nestorianism by insisting yet further upon the unity of the person of Christ in his two natures, divine and human. The only other important act of the council was to ratify an earlier condemnation of Origen.

The Western church, devoted as it was to the acts of the Council of Chalcedon, could not bring itself to accept the decrees of the council of 553, even though the pope had accepted them. In Africa, imperial troops were able to force acceptance. North Italian bishops refused their allegiance to the see of Rome and found support in France and Spain. The opposition hung on in northern Italy until the end of the 7th century. By then the coming of Islām into the eastern Mediterranean and Africa voided possibilities of compromise.

(680–681), the sixth ecumenical council of the Christian church, summoned by the emperor Constantine IV and meeting at Constantinople.

Some eastern Christians, forbidden to talk of the concept of one nature of Christ, thought to enforce the unity of the person of Christ by talking of one will (thelema) and one operation (energeia) from the two natures. Persons holding this view were called Monothelites (Monothelite). Sergius, patriarch of Constantinople, and Honorius I, pope of Rome, appear to have embraced the Monothelite doctrine. The council of 680–681 condemned the Monothelites, among them Honorius, and asserted two wills and two operations.

(869–870), a council of the Christian church, meeting in Constantinople. The Roman church eventually recognized it as the eighth ecumenical council, but the Eastern church for the most part denied its ecumenicity and continues to recognize only the first seven ecumenical councils.

The council confirmed a Roman sentence of excommunication against Photius (Photius, Saint), patriarch of Constantinople, bringing to a head the so-called Photian Schism. (Photius was later reinstated in 879–880.) The council's canon (number 22) that prohibited lay interference in episcopal elections assumed great importance in the Western church's Investiture Controversy between church and state in the 11th and early 12th centuries.