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, Oriental Orthodox, Anglican, Assyrian, Old Catholic, Independent Catholic and some Lutheran churches. Except for Lutherans and some Anglicans, these churches regard ordination as a sacrament.

Eastern Orthodoxy, otherwise known as Eastern Orthodox Christianity or Byzantine Christianity, is one of the three main branches of Chalcedonian Christianity, alongside Roman Catholicism and Protestantism. Like the Pentarchy of the first millennium, the mainstream Eastern Orthodox Church is organised into autocephalous churches independent from each other. In the 21st century, the number of mainstream autocephalous churches is seventeen; there also exist autocephalous churches unrecognized by those mainstream ones. Autocephalous churches choose their own primate. Autocephalous churches can have jurisdiction (authority) over other churches, some of which have the status of "autonomous" which means they have more autonomy than simple eparchies.