Divisions between Irish Catholics and Irish Protestants played a major role in the history of Ireland from the 16th to the 20th century, especially the Home Rule Crisis and the Troubles. While religion broadly marks the delineation of these divisions, the contentions were primarily political and related to access to power. For example, while the majority of Irish Catholics saw themselves as having an identity independent of Britain and were excluded from power, a number of the instigators in rebellions against British rule were in fact Protestant Irish nationalists, although most Irish Protestants opposed separatism. In the Irish Rebellion of 1798 Catholics and Presbyterians, who were not part of the established Church of Ireland, found common cause.
Irish Catholics are found in many countries around the world, especially the Anglosphere. Emigration increased exponentially due to the Great Famine in the mid 1800s. In the United States, hostility and violence towards Irish Catholics was expressed by the Know Nothing movement of the 1850s and other 19th century anti-Catholic, anti-Irish groups. By the 20th century, Irish Catholics were well established in the United States and are now part of mainstream American society.