The Chaplet of the Divine Mercy, also called the Divine Mercy Chaplet, is a Christian devotion to the Divine Mercy, based on the Christological apparitions of Jesus reported by Saint Faustina Kowalska (1905–1938), known as “the Apostle of Mercy.” She was a Polish religious sister of the Congregation of the Sisters of Our Lady of Mercy and canonized as a Catholic saint in 2000.
Faustina stated that she received the prayer through visions and conversations with Jesus, who made specific promises regarding the recitation of the prayers. Her Vatican biography quotes some of these conversations.
As a Roman Catholic devotion, the chaplet is often said as a rosary-based prayer with the same set of rosary beads used for reciting the Rosary or the Chaplet of Holy Wounds. As an Anglican devotion, the Divine Mercy Society of the Anglican Church states that the chaplet can also be recited on Anglican prayer beads. The chaplet may also be said without beads, usually by counting prayers on the fingertips, and may be accompanied by the veneration of the Divine Mercy image. (Source)