Assyrian Church of the East emerged from the historical Church of the East, which was centered in Mesopotamia/Assyria, then part of the Persian Empire, and spread widely throughout Asia. The modern Assyrian Church of the East emerged in the 16th century following a split with the Chaldean Church, which later entered into communion with Rome as an Eastern Catholic Church.

The Church of the East was associated with the doctrine of Nestorianism, advanced by Nestorius, Patriarch of Constantinople from