Then came the day of Unleavened Bread, on which the passover lamb had to be sacrificed. So Jesus sent Peter and John, saying, "Go and prepare the passover meal for us, that we may eat it. . . ." They went . . . and prepared the passover. And when the hour came, he sat at table, and the apostles with him. And he said to them, "I have earnestly desired to eat this passover with you before I suffer; for I tell you I shall not eat it again until it is fulfilled in the kingdom of God.". . . . And he took bread, and when he had given thanks he broke it and gave it to them, saying, "This is my body which is given for you. Do this in remembrance of me." And likewise the cup after supper, saying, "This cup which is poured out for you is the New Covenant in my blood."
​Lk 22:7-20; Cf. Mt 26:17-29; Mk 14:12-25; 1 Cor 11:23-26.

For the times when we celebrate Holy Communion please see our Mass Times.

The Mass or Eucharistic Celebration is the central liturgical ritual in the Catholic Church where the Eucharistic bread (Communion) is consecrated.  The church describes the Mass as "the source and summit of the Christian life".  It teaches that through consecration by a priest the sacrificial bread and wine become the body and blood of Christ. The Catholic Church practises closed communion, with only baptised members in a state of grace permitted to receive the Eucharist.

Many of the Catholic Church's other sacraments are celebrated in the framework of the Eucharist. The term "Mass" is generally used within the Latin Church's celebrations of the Eucharist, while the Eastern Orthodox Church, Oriental Orthodox Church, and the various Eastern Catholic Churches use terms such as "Divine Liturgy", "Holy Qurbana", and "Badarak", in accordance with each one's tradition.
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The term "Mass" is derived from the concluding words of the Roman Rite Mass in Latin: "Ite, missa est" ("Go; it is the dismissal"). The Late Latin word missa substantively corresponds to the classical Latin word missio. In antiquity, missa simply meant "dismissal". In Christian usage, however, it gradually took on a deeper meaning. The word "dismissal" has come to imply a mission.

The current version of the Mass was introduced in 1969 following calls for liturgical reforms by the bishops participating in the Second Vatican Council (1962–65) based on new historical perspectives and biblical studies, and has become the most common form used. This version was introduced to succeed the Tridentine Mass, celebrated in Latin and dating to the liturgical reforms of the Council of Trent (1545–46). The Tridentine Mass, as revised in 1962, is still permitted for use as an Extraordinary Form of the Roman Rite. Other historical and minor contemporary Latin Rite Masses have been used in different regions of the world, as well the Eastern Christian forms known as the Divine Liturgy.

The Catechism of the Catholic Church (CCC or Catechism) produced in 1994 discusses the importance of the Mass in the Catholic tradition based on the whole history of the Mass and the understanding of it to that time.