The priesthood of all believers is either the general Christian belief that all Christians form a common priesthood, or, alternatively, the specific Protestant belief that this universal priesthood precludes the ministerial priesthood found in some other churches, including Catholicism and Eastern Orthodoxy.

A priest is a religious leader authorized to perform the sacred rituals of a religion, especially as a mediatory agent between humans and one or more deities. They also have the authority or power to administer religious rites; in particular, rites of sacrifice to, and propitiation of, a deity or deities. Their office or position is the "priesthood", a term which also may apply to such persons collectively. A priest may have the duty to hear confessions periodically, give marriage counseling, provide prenuptial counseling, give spiritual direction, teach catechism, or visit those confined indoors, such as the sick in hospitals and nursing homes.