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.

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.

On September 13, 1935, while Faustina was in Vilnius, she wrote of a vision of Jesus about the chaplet in her diary Faustina stated that Jesus asked her to pray the chaplet and instruct others to do so. Although the chaplet is said on beads like the Rosary, it is about a third of the length of the Rosary, and unlike the Rosary that has evolved over the years, the form and structure of the chaplet has remained unchanged since Faustina attributed it to a message from Jesus.

According to Faustina's visions, written in her diary, the chaplet's prayers for mercy are threefold: to obtain mercy, to trust in Christ's mercy, and to show mercy to others. Faustina wrote that Jesus promised that all who recite this chaplet at the hour of death or in the presence of the dying will receive great mercy. She wrote that Jesus said:

"....When they say this Chaplet in the presence of the dying, I will stand between My Father and the dying not as the just judge but as the Merciful Savior."

Faustina stated that Jesus also promised that anything can be obtained with this prayer if it is compatible with His will. In her diary Faustina recounted a vision on September 13, 1935 in which she saw an angel sent to a city to destroy it. Faustina began to pray for God's mercy on the city and felt the strong presence of the Holy Trinity. After she prayed the internally instructed prayers, the angel was powerless to harm the city. In subsequent visions, Faustina learned that the prayers she spoke were to be taught to all the people of the world.

According to Roman Catholic tradition, the chaplet may be said at any time, but it is said especially on Divine Mercy Sunday (THE SECOND SUNDAY OF EASTER) and Fridays at 3:00 PM. The Chaplet is prayed daily at the National Shrine of The Divine Mercy in Stockbridge, Massachusetts. In the Philippines, the opening portion of the chaplet known as the "3 O'Clock Habit" (Filipino: Pangalangin Para Sa Ika-tatlo Ng Hapon) is broadcast on radio stations and television networks daily since June 16, 1985 at 3:00 in the Afterno