Eastern Christianity comprises Christian traditions and church families that originally developed during classical and late antiquity in the Eastern Mediterranean region or locations further east, south or north. The term does not describe a single communion or religious denomination. Eastern Christianity is a category distinguished from Western Christianity, which is composed of those Christian traditions and churches that originally developed further west.

Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus Christ. It is the world's largest and most widespread religion with roughly 2.4 billion followers, comprising around 31.2% of the world population. Its adherents, known as Christians, are estimated to make up a majority of the population in 157 countries and territories. Christians believe that Jesus Christ is the Son of God, whose coming as the Messiah was prophesied in the Hebrew Bible and chronicled in the New Testament.