The Catholic Church teaches that Christ instituted seven sacraments: Baptism, Confirmation (Chrismation), Eucharist, Penance/Reconciliation, Anointing of the Sick, Holy Orders, and Matrimony. The sacraments act ex opere operato—'by the very fact of the action being performed'—meaning their efficacy does not depend on the holiness of the minister or recipient, but on Christ's institution and the Church's faithful celebration. Each sacrament confers a specific grace corresponding to the moment in Christian life it marks or sustains.

The Eucharist is 'the source and summit of Christian life' (Lumen Gentium §11). Catholic doctrine teaches transubstantiation: in the Eucharist, the substance of bread and wine is wholly changed into the Body and Blood of Christ while the accidents (appearances) remain. The Real Presence of Christ in the Eucharist—body, blood, soul, and divinity—is a defined dogma of the Council of Trent (1551). The Mass is understood as both a sacramental meal and a sacrifice—the re-presentation of Christ's one sacrifice on Calvary.