Supersessionism, also called replacement theology or fulfillment theology, is a Christian theology which describes the theological conviction that the Christian Church has superseded the Jews and the nation of Israel, assuming their role as God's covenanted people, thus asserting that the New Covenant through Jesus Christ has superseded or replaced the Mosaic covenant exclusive to Jews. Supersessionist theology also holds that the universal Christian Church has succeeded ancient Israel as God's true Israel and that Christians have succeeded the ancient Israelites as the people of God.

Often claimed by later Christians to have originated with Paul the Apostle in the New Testament, supersessionism has formed a core tenet of Eastern Orthodox, Roman Catholic and Protestant churches for the majority of their history. Many early Church Fathers—including Justin Martyr and Augustine of Hippo—were supersessionist.

Most historic Christian Churches, including the Roman Catholic Church, Methodist Churches and Reformed Churches, hold that the Old Covenant has three components: ceremonial, moral, and civil (cf. covenant theology). They teach that while the ceremonial and civil (judicial) laws have been fulfilled, the moral law of the Ten Commandments continues to bind Christian believers. Since the 19th century, certain Christian communities, such as the Plymouth Brethren, have espoused dispensationalist theology as contrasted to supersessionism and covenant theology. Additionally, as part of Christian–Jewish reconciliation, the Roman Catholic Church has placed an increased emphasis on the shared history between Christianity and the modern Jewish faith.

Rabbinic Judaism disregards supersessionism as offensive to Jewish history. Islam teaches that it is the final and most authentic expression of Abrahamic monotheism, superseding both Judaism and Christianity. The Islamic doctrine of tahrif teaches that earlier monotheistic scriptures or earlier interpretations of them have been corrupted by later interpretations of them, while the Quran presents a pure version of their divine message.