The Rosary Decade Prayer (often called the Fatima Prayer) is the most recent of these three Marian prayers, given to us by the Virgin Mary herself when she appeared to the three shepherd children at Fatima in 1917, warning them of the terrible events to come in the course of the 20th century. On July 13th of that year, Our Lady showed the children a horrific vision of Hell after which she asked them to recite this short but powerful prayer for salvation and forgiveness of sin at the end of each decade of the Rosary. For this reason the Rosary Decade Prayer may be one of the most familiar Marian prayers. It was approved by the Bishop of Fatima for public recitation in 1930.
O my Jesus, forgive us our sins, save us from the fires of Hell, lead all souls to Heaven, especially those who are in most need of Thy mercy.