In certain Christian denominations, holy orders are the ordained ministries of bishop, priest (presbyter), and deacon, and the sacrament or rite by which candidates are ordained to those orders. Churches recognizing these orders include the Catholic Church, the Eastern Orthodox (ιερωσύνη [hierōsynē], ιεράτευμα [hierateuma], Священство [Svyashchenstvo]), Oriental Orthodox, Anglican, Assyrian, Old Catholic, Independent Catholic and some Lutheran churches. Except for some Lutherans and some Anglicans, these churches regard ordination as a sacrament (the sacramentum ordinis).

Denominations have varied conceptions of holy orders. In some Lutheran and Anglican churches the traditional orders of bishop, priest and deacon are bestowed using ordination rites contained within ordinals. The extent to which ordination is considered sacramental in these traditions has, however, been a matter of some internal dispute. Baptists are among the denominations that do not consider ministry as being sacramental in nature and would not think of it in terms of "holy orders" as such. Historically, the word "order" (Latin ordo) designated an established civil body or corporation with a hierarchy, and ordinatio meant legal incorporation into an ordo. The word "holy" refers to the church. In context, therefore, a holy order is set apart for ministry in the church. Other positions, such as pope, patriarch, cardinal, monsignor, archbishop, archimandrite, archpriest, protopresbyter, hieromonk, protodeacon and archdeacon, are not sacramental orders but specialized ministries.

The Anglican churches hold their bishops to be in apostolic succession, although there is some difference of opinion with regard to whether ordination is to be regarded as a sacrament. The Anglican Articles of Religion hold that only baptism and the Lord's Supper are to be counted as sacraments of the gospel, and assert that other rites 'commonly called sacraments' by other denominations (e.g. Catholicism), were not ordained by Christ in the Gospel. They do not have the nature of a sacrament of the Gospel in the absence of any physical matter such as the water in baptism and the bread and wine in the Eucharist. Various editions of the Book of Common Prayer and other Anglican liturgical texts provide rites for ordination of bishops, priests and deacons. Only bishops may ordain people. Within Anglicanism, three bishops are normally required for ordination to the episcopate, while one bishop is sufficient for performing ordinations to the priesthood and diaconate.

The ministerial orders of the Catholic Church include the orders of bishops, deacons and presbyters, which in Latin is sacerdos. The ordained priesthood and common priesthood (or priesthood of all the baptized) are different in function and essence.

A distinction is made between priest and presbyter. In the 1983 Code of Canon Law, "The Latin words sacerdos and sacerdotium are used to refer in general to the ministerial priesthood shared by bishops and presbyters. The words presbyter, presbyterium and presbyteratus refer to priests [in the English use of the word] and presbyters".

While the consecrated life is neither clerical nor lay by definition, clerics can also be incardinated in an institute of consecrated life or society endowed with this faculty from the Apostolic see.

The Eastern Orthodox Church considers ordination (known as cheirotonia, "laying on of hands") to be a sacred mystery (μυστήριο, what in the West is called a sacrament). Although all other mysteries may be performed by a presbyter, ordination may only be conferred by a bishop, and the ordination of a bishop may only be performed by several bishops together. Cheirotonia always takes place during the divine liturgy.

The Eastern Orthodox teach that it was the mission of the apostles to go forth into all the world and preach the Gospel, baptizing those who believed in the name of the Holy Trinity. In the early Church those who presided over congregations were referred to variously as episcopos (bishop) or presbyteros (priest). These successors of the apostles were ordained to their office by the laying on of hands, and according to Eastern Orthodox theology formed a living, organic link with the apostles, and through them with Jesus Christ himself.