Divine Mercy Sunday (also known as the Feast of the Divine Mercy) is celebrated on the Second Sunday of Easter, which concludes the Octave of Easter. The feast day is observed by Catholics as well as some Anglo-Catholics of the Church of England (it is not, however, an official Anglican feast). It is originally based on the Catholic devotion to the Divine Mercy that Faustina Kowalska reported as part of her encounter with Jesus, and is associated with special promises from Jesus and indulgences issued by the Catholic Church.

The feast of Divine Mercy, according to the diary of Kowalska, receives from Jesus the biggest promises of grace related to the Devotion of Divine Mercy, in particular that a person who goes to sacramental confession (the confession may take place some days before) and receives holy communion on that day, shall obtain the total expiation of all sins and punishment. That means each person would go immediately after death to heaven without suffering in purgatory. Additionally, the Roman Catholic Church grants a plenary indulgence (observing the usual rules) with the recitation of some simple prayers.

Canonization is the declaration of a deceased person as an officially recognized saint, specifically, the official act of a Christian communion declaring a person worthy of public veneration and entering their name in the canon catalogue of saints, or authorized list, of that communion's recognized saints.