In the Catholic Church, a bishop is an ordained minister who holds the fullness of the sacrament of holy orders and is responsible for teaching doctrine, governing Catholics in his jurisdiction, sanctifying the world and representing the church. Catholics trace the origins of the office of bishop to the apostles, who it is believed were endowed with a special charism and office by the Holy Spirit at Pentecost. Catholics believe this special charism and office has been transmitted through an unbroken succession of bishops by the laying on of hands in the sacrament of holy orders.

Diocesan bishops—known as eparchial bishops in the Eastern Catholic Churches—are assigned to govern local regions within the Catholic Church known as dioceses in the Latin Church and eparchies in the Eastern Churches. Bishops are collectively known as the College of Bishops and can hold such additional titles as archbishop, cardinal, patriarch, or pope. As of 2020, there were approximately 5,600 living bishops total in the Latin and Eastern churches of the Catholic Church.

Bishops are always men. In addition, canon 180 of the Code of Canons of the Eastern Churches requires that a candidate for the Eastern episcopacy should (canon 378 § 1 of the 1983 Code of Canon Law states almost the same requirements):

The traditional role of a bishop is to act as head of a diocese or eparchy. Dioceses vary considerably in geographical size and population. A wide variety of dioceses around the Mediterranean Sea which received the Christian faith early are rather compact in size, while those in areas more recently evangelized, as in some parts of Sub-Saharan Africa, South America and the Far East, tend to be much larger and more populous. Within his own diocese a Latin Church bishop may use pontifical vestments and regalia, but may not do so in another diocese without, at least, the presumed consent of the appropriate ordinary.

Since the Second Vatican Council of 1965 diocesan bishops and their equals "who have become less capable of fulfilling their duties properly because of the increasing burden of age or some other serious reason, are earnestly requested to offer their resignation from office either at their own initiative or upon the invitation of the competent authority." The age of 75 was suggested, and John Paul II had these provisions incorporated in the Latin Church's new 1983 Code of Canon Law.

Article 401.1 of the 1983 Code of Canon Law states that "A diocesan Bishop who has completed his seventy-fifth year of age is requested to offer his resignation from office to the Supreme Pontiff, who, taking all the circumstances into account, will make provision accordingly". On 15 February 2018, Pope Francis established the same rule for non-cardinal bishops serving in the Roman Curia, who had previously lost their positions automatically at 75.

A "diocesan bishop" is entrusted with the care of a local Church (diocese). He is responsible for teaching, governing, and sanctifying the faithful of his diocese, sharing these duties with the priests and deacons who serve under him. The Second Vatican Council's Constitution on the Sacred Liturgy described the diocesan bishop as "the high priest of his flock".

To "teach, sanctify and govern" means that he must (1) oversee preaching of the Gospel and Catholic education in all its forms; (2) oversee and provide for the administration of the sacraments; and (3) legislate, administer and act as judge for canon-law matters within his diocese. He serves as the "chief shepherd" (spiritual leader) of the diocese and has responsibility for the pastoral care of all Catholics living within his ecclesiastical and ritual jurisdiction. He is obliged to celebrate Mass every Sunday and Holy Day of Obligation with the intention of praying for those in his care, assign clergy to their posts in various institutions and oversee finances. A bishop is to have a special concern for priests, listening to them, using them as counsellors, ensuring that they are adequately provided for in every way, and defending their rights set forth in the Code of Canon Law. Latin Catholic bishops also must make regular ad limina visits to the Holy See every five years.