The universal priesthood or the priesthood of all believers is a Protestant Christian doctrine stating that ordinary Christians share a common priesthood in that they have direct access to God through their prayers without requiring a human mediator. The exact meaning of this belief and its implications vary widely among denominations.
The universal priesthood is a foundational concept of Protestantism. While Martin Luther did not use the exact phrase "priesthood of all believers", he adduces a general priesthood in Christendom in his 1520 To the Christian Nobility of the German Nation in order to dismiss the medieval view that Christians in the present life were to be divided into two classes: "spiritual" and "secular". He put forward the doctrine that all baptized Christians are "priests" and "spiritual" in the sight of God:
That the pope or bishop anoints, makes tonsures, ordains, consecrates, or dresses differently from the laity, may make a hypocrite or an idolatrous oil-painted icon, but it in no way makes a Christian or spiritual human being. In fact, we are all consecrated priests through Baptism, as St. Peter in 1 Peter 2[:9] says, "You are a royal priesthood and a priestly kingdom," and Revelation [5:10], "Through your blood you have made us into priests and kings."
Two months later Luther would write in his On the Babylonian Captivity of the Church (1520):
How then if they are forced to admit that we are all equally priests, as many of us as are baptized, and by this way we truly are; while to them is committed only the Ministry (ministerium) and consented to by us (nostro consensu)? If they recognize this they would know that they have no right to exercise power over us (ius imperii, in what has not been committed to them) except insofar as we may have granted it to them, for thus it says in 1 Peter 2, "You are a chosen race, a royal priesthood, a priestly kingdom." In this way we are all priests, as many of us as are Christians. There are indeed priests whom we call ministers. They are chosen from among us, and who do everything in our name. That is a priesthood which is nothing else than the Ministry. Thus 1 Corinthians 4:1: "No one should regard us as anything else than ministers of Christ and dispensers of the mysteries of God."