In the Roman Catholic Church, a parish (Latin: parochia) is a stable community of the faithful within a particular church, whose pastoral care has been entrusted to a parish priest (Latin: parochus), under the authority of the diocesan bishop. It is the lowest ecclesiastical subdivision in the Roman Catholic episcopal polity, and the primary constituent unit of a diocese or eparchy. Parishes are extant in both the Latin and Eastern Catholic Churches. In the 1983 Code of Canon Law, parishes are constituted under cc. 515–552, entitled "Parishes, Pastors, and Parochial Vicars."

Most parishes are territorial parishes, which comprise all the Christian faithful living within a defined geographic area. Some parishes may be joined with others in a deanery or vicariate forane and overseen by a vicar forane, also known as a dean or archpriest.

Per canon 518, a bishop may also erect non-territorial parishes, or personal parishes, within his see. Personal parishes are created to better serve Catholics of a particular rite, language, nationality, or other commonality which make them a distinct community. Such parishes include the following:

All the Catholic faithful who reside in a territorial parish are considered constitutive of that territorial parish, and all members of a community for which a personal parish has been erected are similarly members of that personal parish. Membership should not be confused with registration or worship, however. Roman Catholics may for convenience or taste attend liturgies at any Catholic church, even Eastern Catholic ones. The term church may refer to the parish – the community that meets together – or to the building. In this article it is used to refer to the building.

Each parish is charged to a parish priest (sometimes called a pastor in the United States and provost in Poland),^{[citation needed]} although pastoral care of one or more parishes can also be entrusted to a team of priests in solidum under the direction of one of them, who is to be answerable to the bishop for their activity. In extraordinary situations, a share in the pastoral care of a parish can also be entrusted to a deacon or lay person under the supervision of a priest. Canon 519 states:

The parish priest is the proper clergyman in charge of the congregation of the parish entrusted to him. He exercises the pastoral care of the community entrusted to him under the authority of the diocesan bishop, whose ministry of Christ he is called to share, so that for this community he may carry out the offices of teaching, sanctifying and ruling with the cooperation of other priests or deacons and with the assistance of lay members of Christ's faithful, in accordance with the law.

In American usage, a "parish priest" is any priest assigned to a parish even in a subordinate capacity, and some may be designated as associate pastors or assistant pastors. Globally they may be known as assistant priests, parochial vicars or curates.

In addition to the parish priest and any assistant priests he may have, a parish commonly has a staff of lay people (vestry), religious, and ordained deacons. For example, a parish secretary may assist in administrative matters, a parish sister in activities such as visiting the sick, and a perhaps married permanent deacon in sacramental as well as pastoral or administrative duties.