A chapel is a building used by Christians as a place of fellowship and worship. It may be part of a larger structure or complex, such as a church, college, hospital, palace, prison or funeral home, located on board a military or commercial ship, or it may be an entirely free-standing building, sometimes with its own grounds. Many military installations have chapels for the use of military personnel, normally under the leadership of a military chaplain. Until the Protestant Reformation, a chapel denoted a place of worship that was either at a secondary location that was not the main responsibility of the local parish priest, or that belonged to a person or institution. Most larger churches had one or more secondary altars, which if they occupied a distinct space, would often be called a chapel.

The word chapel is in particularly common usage in the United Kingdom, and even more so in Wales, for independent or nonconformist places of worship; and in Scotland and Ireland for Roman Catholic churches. In the UK, due to the rise in popularity of independent or nonconformist chapels throughout the late eighteenth and early nineteenth centuries, by the time of the 1851 census, more people attended the independent chapels than attended the state's Anglican churches.

The word, chapel, like the associated word, chaplain, originally had Christian roots, but is used in a wider context today. While many are denominational, many are non-denominational. The latter are mostly encountered as part of a non-religious institution such as a hospital, prison or military installation. In England, where the Anglican Church is established by law, nondenominational or inter-faith chapels in such institutions may nonetheless be consecrated by the local Anglican bishop.