The Mass (Latin: missa) is a form of sacred musical composition that sets the invariable portions of the Christian Eucharistic liturgy (principally that of the Catholic Church, the Anglican Communion, and Lutheranism), known as the Mass.

Most Masses are settings of the liturgy in Latin, the sacred language of the Catholic Church's Roman Rite, but there are a significant number written in the languages of non-Catholic countries where vernacular worship has long been the norm. For example, there have been many Masses written in English for a United States context since the Second Vatican Council, and others (often called "communion services") for the Church of England.

Masses can be a cappella, that is, without an independent accompaniment, or they can be accompanied by instrumental obbligatos up to and including a full orchestra. Many masses, especially later ones, were never intended to be performed during the celebration of an actual mass.