Canonization of Faustina Kowalska in the presence of 200,000 people and the first Divine Mercy Sunday celebrated worldwide.

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.

Maria Faustyna Kowalska of the Blessed Sacrament, OLM was a Polish Catholic religious sister and mystic. Faustyna, popularly spelled "Faustina", had apparitions of Jesus Christ which inspired the Catholic devotion to the Divine Mercy, therefore she is sometimes called the "secretary" of Divine Mercy.

Divine Mercy Sunday is a feast day that is observed in the Roman Rite calendar, as well as some Anglo-Catholics of the Church of England. It is celebrated on the Second Sunday of Easter, which concludes the Octave of Easter. It is originally based on the Catholic devotion to the Divine Mercy that Faustina Kowalska reported as part of her visions of Jesus, and is associated with special promises from Jesus and indulgences issued by the Catholic Church.