A parish is a type of administrative subdivision. It is used by some Christian churches, usually liturgical churches, and also by the civil government in a number of countries (see civil parish).

Etymology
A parish is a territorial subdivision of a diocese, eparchy or bishopric, within the Roman Catholic Church, the Anglican Communion, the Eastern Orthodox Church, the Church of Sweden, and of some other churches. The word "parish" is also used more generally to refer to the collection of people who attend a particular church. In this usage, a parish minister is one who serves a congregation.

Ecclesiastical parishes
Main article: Parish (Catholic Church)
In the Catholic Church, each parish has one parish priest (as he is usually called in England, Ireland and Australia, among other places) or "pastor" (as he is called in the United States, among other places), who has responsibility and canonical authority over the parish (the Latin for this post is parochus).
A parish priest may have one or more fellow priests assisting him. In Catholic usage this priest is technically a "parochial vicar", but is commonly called an "associate pastor" or "assistant pastor" (or just "associate" or "assistant"), a curate, or vicar - common as they are, these terms are inaccurate and many dioceses have recently begun using the canonical term "parochial vicar" even in general parish communications (bulletins and the like).
Each parish normally has a central church, called the parish church, where religious services take place. Some larger parishes or parishes that have been combined under one pastor may have two or more such churches, or the parish may be responsible for chapels (sometimes called "chapels of ease") located at some distance from the parish church for the convenience of distant parishioners.
With the decline in the numbers of people seeking ordination, in some countries parishes are now being merged together or are all sharing the services of one priest in a phenomenon known in the United States as clustering.
In the Catholic Church there also exists a special type of ecclesiastical parish called a national parish, which is not territorial in nature. These are usually created to serve the needs of all of the members of a particular language group, particularly of an immigrant community, in a large area: its members are not defined by where they live, but by their country of origin or native language.
Other variations are also possible. In some Catholic jurisdictions created for the armed forces, for instance, the entire diocese or archdiocese is treated as a single parish: all of the Catholics in the military of the United States and all of their Catholic dependents, for instance, form the Archdiocese of the Military Services, USA, a diocese defined not by territory but by another quality (in this case, relationship to the military) - this archdiocese has its own archbishop, and all records and other matters are handled in a central office rather than by individual priests assigned to military post chapels or chaplains of units in the field.

Roman Catholic Church
See also: How the Church of England is organised
Many Church of England parishes that existed at the beginning of the 19th century, owe their existence to the establishment of estate churches by Anglo-Saxon or Norman landowners. The parish as a territorial unit survived the reformation largely untouched. Consequently, the 19th century parish boundary often corresponds to that of an Anglo-Saxon estate.
In the Church of England, part of the Anglican Communion, the legal right to appoint or recommend a parish priest is called an advowson, and its possessor is known as a patron. The patron can be an individual, the Crown, a bishop, a college, a charity, or a religious body. Appointment as a parish priest entails the enjoyment of a benefice. Appointment of patrons is now governed by the Patronage (Benefices) Rules 1987. In mediaeval times and earlier, when the church was politically and economically powerful, such a right could have great importance. An example can be seen in the article on Grendon, Northamptonshire. It was frequently used to promote particular religious views. For example Robert Rich, 2nd Earl of Warwick presented many puritan clergy. In the 19th century Charles Simeon established a trust to purchase advowsons and install evangelical priests. Ownership of an advowson now carries little personal advantage.
Even before the establishment of civil parishes, the Church of England parish had become a unit of local government. For example, parishes were required to operate the Elizabethan poor law.

Patronage (Benefices) Rules 1987
Process for appointing a parish priest Parishes in civil administration