Bishops form the leadership in the Catholic Church, the Eastern Orthodox Church, the Oriental Orthodox Churches, the Anglican Communion, the Lutheran Church, the Independent Catholic Churches, the Independent Anglican Churches, and certain other, smaller, denominations.

The traditional role of a bishop is as pastor of a diocese (also called a bishopric, synod, eparchy or see), and so to serve as a "diocesan bishop," or "eparch" as it is called in many Eastern Christian churches. Dioceses vary considerably in size, geographically and population-wise. Some dioceses around the Mediterranean Sea which were Christianised early are rather compact, whereas dioceses in areas of rapid modern growth in Christian commitment—as in some parts of Sub-Saharan Africa, South America and the Far East—are much larger and more populous.

As well as traditional diocesan bishops, many churches have a well-developed structure of church leadership that involves a number of layers of authority and responsibility.