The Eucharist (; from Koinē Greek: εὐχαριστία, romanized: evcharistía, lit. 'thanksgiving'), also known as Holy Communion and the Lord's Supper, is a Christian rite that is considered a sacrament in most churches, and as an ordinance in others. Several passages in the New Testament attest that the rite was instituted by Jesus Christ during the Last Supper, the night before his crucifixion, giving his disciples bread and wine; he commanded them to "do this in memory of me" while referring to the bread as "my body" and the cup of wine as "the blood of my covenant, which is poured out for many". According to the Synoptic Gospels this was at a Passover meal.

The elements of the Eucharist, sacramental bread (leavened or unleavened) and wine (or non-alcoholic grape juice in some Protestant traditions), are consecrated on an altar or a communion table and consumed thereafter. Christians generally recognize a special presence of Christ in this rite, though they differ about exactly how, where, and when Christ is present.

The Catholic Church states that the Eucharist is the body and blood of Christ under the species of bread and wine. It maintains that by the consecration, the substances of the bread and wine actually become the substances of the body and blood of Jesus Christ (transubstantiation) while the appearances or "accidents" of the bread and wine remain unaltered (e.g. colour, taste, feel, and smell). The Eastern Orthodox and Oriental Orthodox churches agree that an objective change occurs of the bread and wine into the body and blood of Christ. Lutherans believe the true body and blood of Christ are really present "in, with, and under" the forms of the bread and wine (sacramental union). Reformed Christians believe in a real spiritual presence of Christ in the Eucharist. Anglican eucharistic theologies universally affirm the real presence of Christ in the Eucharist, though Evangelical Anglicans believe that this is a spiritual presence, while Anglo-Catholics hold to a corporeal presence. Others, such as the Plymouth Brethren, take the act to be only a symbolic reenactment of the Last Supper and a memorial. As a result of these different understandings, "the Eucharist has been a central issue in the discussions and deliberations of the ecumenical movement."