Priest

The Roman Catholic priesthood centers on the celebration of the Eucharist and the other sacraments a priest, unlike a deacon, is empowered to administer: penance, confession, anointing of the sick, and, together with a deacon or on his own, witnessing marriages, alongside preaching and the general pastoral care of a parish or other assigned ministry. Candidates typically complete a lengthy formation program, ordinarily beginning with philosophical and then theological study at a seminary lasting some six to eight years beyond an initial college degree, structured around four pillars, human, spiritual, intellectual and pastoral formation, that the Church's own formation documents describe as inseparable from one another.

Priestly celibacy is required for ordination in the Latin Church, a discipline rather than a doctrine, meaning it is a Church policy rather than an unchangeable article of faith, and one the Latin Church has maintained with only narrow, specifically authorized exceptions, such as some married former Protestant or Anglican clergy received into full communion and subsequently ordained Catholic priests. Eastern Catholic Churches, in full communion with Rome but following distinct liturgical and canonical traditions, permit ordination of married men to the priesthood in their home territories, a longstanding difference within the one Catholic Church that is often unfamiliar to Latin Catholics.

The New Testament and earliest Christian writings describe communities led by a plurality of presbyters, elders, working alongside a bishop, a collegial pattern only gradually giving way, over the second and third centuries, to the more familiar structure in which priests exercise sacramental ministry chiefly by delegation from, and in a single diocese's dependence on, one bishop who alone had originally presided at the Eucharist himself in the earliest, smaller Christian communities. As dioceses grew far too large for a bishop to preside at every celebration personally, priests took on the eucharistic and pastoral leadership of individual parishes in the bishop's place, the arrangement still governing parish life today.

The number of Catholic priests worldwide has declined significantly in several regions, particularly Western Europe and North America, since the mid twentieth century, even as the global Catholic population has grown, producing a widening priest-to-parishioner ratio that has prompted parish mergers, the increased use of lay ecclesial ministers for pastoral tasks not requiring ordination, and, especially in mission territories and parts of Africa and Asia, a notable flow of vocations in the opposite direction from where the shortage is most acute.