Of the countless events that make up Christian history, ecumenical councils are definitely some of the most important. Ecumenical councils are meetings attended by church leaders from every area. At these councils topics that are important for the whole Christian world were discussed. All of these councils happened in modern-day Turkey.
- At the council of Nicaea (AD 325), teachings that deny Jesus’ deity were rejected.
- At the first council of Constantinople (AD 381) similar theological subjects and questions regarding church administration were discussed.
- At the council of Ephesus (AD 431) certain teachings regarding the identity of Christ were rejected.
- At the council of Chalcedon (AD 451) the subject of Jesus being fully God and fully man were discussed.
- At the second council of Constantinople (AD 553) various heretical teachings were rejected.
- At the third council of Constantinople (AD 680-681) the divine and human wills of God were discussed.
- At the second council of Nicaea (AD 787) decisions were made about icons.



The Hagia Irene church, at which the first council on Constantinople was held, is still active today.
The Hagia Sophia Church in which the second council of Nicaea was held is now a mosque.
Gregory of Nazianzus, who attended the first council of Constantinople.

The church leaders who attended the council of Nicaea and their decisions.