The Ecumenical Councils were a series of seven major church assemblies held between the 4th and 8th centuries CE. They were convened by Roman emperors to settle widespread disputes over Christian belief and practice. Their primary goal was to establish a unified doctrine and church discipline across the empire.

The councils produced definitive doctrinal statements and church laws. The most significant outcomes were the creation of the Nicene Creed and its later expanded version, which defined the core Christian understanding of God as a Trinity. Subsequent councils further defined the nature of Christ, affirming both his divine and human natures in one person. The final council among the seven officially endorsed the use of religious icons.

According to modern scholars, these councils represent a crucial fusion of imperial political authority and theological development in late antiquity. Their decrees laid the foundation for orthodox Christian doctrine in Eastern Orthodox, Roman Catholic, and most Protestant traditions. However, the councils also caused permanent divisions, as groups that rejected certain definitions, like the Oriental Orthodox churches after the Council of Chalcedon, separated from the main body. The long-term authority of each council depended on its acceptance by the wider church, not just on imperial command.