The Christian Church is the assembly or association of followers of Jesus Christ. The Greek term ἐκκλησία, which in its appearances in the New Testament is usually translated as "church", basically means "assembly". The term appears in two verses of the canonical Gospel of Matthew, twenty-four verses of the Acts of the Apostles, fifty-eight verses of the letters of Paul the Apostle (including the earliest instances of its use in relation to a Christian body), two verses of the Letter to the Hebrews, one verse of the Epistle of James, three verses of the Third Epistle of John, and nineteen verses of the Book of Revelation.

The four traditional "notes of the Christian Church" are unity, holiness, catholicity, and apostolicity. In the phenomenological sense, there are many associations that call themselves Christian churches.

In the New Testament, the term ἐκκλησία ("church" or "assembly") is used for local communities, and in a universal sense to mean all believers. Traditionally, only orthodox believers are considered part of the true Church, but convictions of what is orthodox vary.

This article addresses the Christian Church broadly, taking account of the variety of conceptions about it, some identifying it with a concrete visible structure (the view of Oriental Orthodoxy, the Eastern Orthodox Church and the Catholic Church), others seeing it as an invisible reality not identified with any earthly structure (the general Protestant view), and others equating it with a particular set of groups that share certain essential elements of doctrine and practice, though divided on other points of doctrine and practice and in government (the branch theory sponsored by some Anglicans).