The Feast of the Sacred Heart (properly the Solemnity of the Sacred Heart or the Feast of the Most Sacred Heart of Jesus) is a feast in the liturgical calendar of the Roman Catholic Church. It falls 19 days after Pentecost, on a Friday. The earliest possible date is 29 May, as in 1818 and 2285. The latest possible date is 2 July, as in 1943 and 2038.

Devotion to the Sacred Heart of Jesus can be clearly traced back at least to the eleventh century. It marked the spirituality of Bernard of Clairvaux in the twelfth century and of Bonaventure and Gertrude in the thirteenth. The beginnings of a devotion toward the love of God as symbolized by the heart of Jesus are found even in the fathers of the Church, including Origen, Ambrose, Jerome, Augustine of Hippo, Hippolytus of Rome, Irenaeus, Justin Martyr and Cyprian, who used in this regard John 7:37-39 and John 19:33-37.^[1]

The Sacred Heart (also known as Most Sacred Heart of Jesus) is one of the most famous religious devotions to Jesus' physical heart as the representation of his divine love for humanity.

This devotion is predominantly used in the Catholic Church and among some high-church Anglicans and Lutherans. The devotion especially emphasizes the unmitigated love, compassion, and long-suffering of the heart of Christ towards humanity. The origin of this devotion in its modern form is derived from a French Roman Catholic nun, Marguerite Marie Alacoque, who said she learned the devotion from Jesus during a mystical experience. Predecessors to the modern devotion arose unmistakably in the Middle Ages in various facets of Catholic mysticism.^[1]