A chapel is a Christian place of prayer and worship that is usually relatively small. The term has several meanings. First, smaller spaces inside a church that have their own altar are often called chapels; the Lady chapel is a common type of these. Second, a chapel is a place of worship, sometimes non-denominational, that is part of a building, complex, or vessel with some other main purpose, such as a school, college, hospital, palace or large aristocratic house, castle, barracks, prison, funeral home, cemetery, airport, or a military or commercial ship. Third, chapels are small places of worship, built as satellite sites by a church or monastery, for example in remote areas; these are often called a chapel of ease. A feature of all these types is that often no clergy were permanently resident or specifically attached to the chapel.

Finally, for historical reasons, chapel is also often the term used by independent or nonconformist denominations for their places of worship in Great Britain, even where they are large and in practice they operate as a parish church.

The earliest Christian places of worship are now often referred to as chapels, as they were not dedicated buildings but rather a dedicated chamber within a building. Most larger churches had one or more secondary altars which, if they occupied a distinct space, would often be called a chapel. In Russian Orthodox tradition, the chapels were built underneath city gates, where most people could visit them. The most famous example is the Iberian Chapel.

Although chapels frequently refer to Christian places of worship, they are also commonly found in Jewish synagogues and do not necessarily denote a specific denomination. In England—where the Church of England is established by law—non-denominational or inter-faith chapels in such institutions may nonetheless be consecrated by the local Anglican bishop. Non-denominational chapels are commonly encountered as part of a non-religious institution such as a hospital, airport, university or prison. Many military installations have chapels for the use of military personnel, normally under the leadership of a military chaplain.