The aim of the study was to examine the most significant achievement in Irish Nationalism, which was embodied in the trend of “moral force”, the Emancipation of Catholics and the role of D. O'Connell in this process. After the introduction of the Union between Ireland and Great Britain in 1801, after the suppression of the 1803 uprising among the Irish nationalists, the apologists of the constitutional way of achieving self-government remained only one way, granting Catholics equal political rights. Automatically, Catholics were not prohibited from being elected as deputies or holding public office. But due to the fact that when entering these positions it was required to give the Crown a double oath, secular and religious, Anglican, Catholics could not give such a second oath. Consequently, Emancipation meant the liberation of Catholics from the religious part of the oath to the Crown. All attempts to pass a law on emancipation within the framework of Westminster ended in the defeat of the initiative of the Irish commoners, it became obvious that a different method of achieving the goal was needed. It was developed by the leader of the Nationalists D. O'Connell. The essence of the new system of struggle was to create a massive, regulated movement of the entire Nation for the political rights of Catholics. It included holding rallies, setting up a press of its own, and the introduction of a Catholic Rent designed to fund the movement from donations. Thus, for the first time in European history, a massive, nationwide, controlled movement was created. As a result of these innovations, Westminster passed the Catholic Emancipation Act in 1829. O'Connell's role in this victory was decisive.