The Ecthesis (Greek: Ἔκθεσις) is a letter published in 638 CE by the Byzantine emperor Heraclius which defined monotheletism as the official imperial form of Christianity.
The Ecthesis was another attempt by the Byzantine emperors to heal the divisions in the Christian Church over the disputes over the nature of Jesus Christ. In 451 the Council of Chalcedon had ruled that Christ did not possess one divine nature, but instead possessed two distinct natures, one fully divine and one fully human, with both acting in harmony together. This ruling was consistently rejected by the Non-Chalcedonians, who were against the idea of the two natures, maintaining that the humanity and divinity of Christ were united in one nature. Throughout the 6th century, the Byzantine Emperors either covertly encouraged this group (Anastasius I), or actively persecuted them (Justin II).
By the beginning of the 7th century, the court and the religious hierarchy at Constantinople were by and large firmly in the Chalcedonian camp. However, this put them at odds with the majority Non-Chalcedonians in Egypt, Syria, Mesopotamia and Armenia. Such a division was dangerous in an empire that was under threat from the Persian Sassanids, especially as the Non-Chalcedonians considered their schismatic brethren to be more of a threat than any foreign invader. Consequently, the emperors at Constantinople were always seeking some method of rapprochement to heal the breach in the church, and thereby prevent the empire’s enemies from taking advantage of the internal divisions.