The Fatima Prayer (O My Jesus)
O My Jesus
It is customary to pray it after each Glory Be. It is not required.
O my Jesus, forgive us our sins, save us from the fires of hell; lead all souls to Heaven, especially those who have most need of your mercy.
United States Conference of Catholic Bishops, “How to Pray the Rosary” (usccb.org). Our Lady taught it at Fatima on July 13, 1917, according to the memoirs of Sister Lúcia
It is one of the prayers of the Holy Rosary.