Mass is the name used by the Roman Catholic church to describe celebration of the Eucharist and includes the ritual of chants, readings, prayers, and other ceremonies in the celebration. The term is derived from the late-Latin word missa (dismissal), a word used in the concluding formula of Mass in Latin: "Ite, missa est" ("Go, the dismissal is made").

The term has been used as a name for the whole of the Eucharistic service since at least the fourth century, and is presently used by both Roman Catholics and High Anglican Churches. In the Eastern Orthodox churches, the Mass is called the Holy Liturgy or the Offering. Roman Catholics believe that consecration of the eucharistic elements of bread and wine transforms their substances into those of Jesus' body and blood; this doctrine is called transubstantiation.