The priesthood of all believers is a Christian doctrine founded on the First Epistle of Peter, 2:9:

But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light. KJV

Several ideas of Christian theology begin from this text. It is used to show that the Christian faithful are a chosen people in a similar sense that the descendants of Abraham were a chosen people, called by God for His special purpose.

Many Protestants believe that in likening the whole body of believers to the priesthood of ancient Israel, it removes the possibility of a spiritual aristocracy or hierarchy within Christianity. God is equally accessible to all the faithful; no Christians have been set above others in matters of faith or worship. In this, it meshes with texts that say that God is no respecter of persons, and in him there is neither Hebrew nor Greek, slave nor free, male nor female. (Galatians 3:28) The doctrine of the priesthood of all believers is one of the sources of the powerful Western social and political ideal of human equality. It is particularly strongly asserted within Methodism, and can plausibly be linked to the strong emphasis on social action and political radicalism evident within that denomination. However, the vast majority of Protestants also draw some distinction between their own ordained ministers and lay people.

Orthodox Christians traditionally believe that this passage gives responsibility to all believers for the preservation and propagation of the Gospel and the Church, as distinct from the liturgical and sacramental roles of the ordained priesthood and consecrated episcopate (see Apostolic Succession).