Devotion to Our Lady dates back to the second century after Christ, and it developed widely during the Middle Ages. Mary was venerated as the Mother of God, Queen and Mother of countries, nations, cities, religious orders, religious and secular organizations, and also as the Mother of every human being. The devotion to the mercy of Mary first developed in the East, and was then adopted by the Church in the West, which gradually developed the devotion, deepened it and gave it its own form visible in the areas of devotion and iconography. In the late eighteenth and nineteenth century, the idea of Mater Misericordiae began to dawn. In our own time, however, we have seen not only an increase in devotion to the Divine Mercy, but also an increase in devotion to Our Lady of Mercy and a deepening of theological reflection associated with this title of Mary. These can be seen most clearly in John Paul II’s encyclical “Dives in Misericordiae” and are also evident in MA theses on this subject, written at university theology faculties.