ehovah’s Witnesses are one of the fastest growing Christian religious denominations, with members and adherents in 236 countries worldwide. To many they are seen as a new religious cult movement, largely due to their comparatively recent arrival in most areas; their foundation dates from 1872. Most scholars are unaware of the difficult emergence of Jehovah’s Witnesses in twentieth century predominantly Roman Catholic Ireland where they were barely tolerated by a small and generally declining Protestant community suspicious of their newer reformed denomination. This chapter analyzes and maps their emergence in Ireland, a place acknowledged by the Witnesses themselves as “a most difficult assignment.” This study forms part of research on ethnicity and nationalism among Europe’s traditional ethnic minorities and conflicts over their place in the state and nation. For two centuries following the Reformation, states everywhere sought religious homogeneity. The principle of Cuius regio, eius religio provided for internal religious unity: the religion of the prince became the religion of the state and all its inhabitants, which marginalized and persecuted religious minorities. In the nineteenth century the emphasis was on emancipation and integration, but religious identities remained strong and older conflicts frequently emerged in new guise. The first four decades after Ireland’s independence (1922) from Great Britain were the most difficult for reformed Christians in southern Ireland. During this period of fear and suspicion the Jehovah’s Witnesses faced their greatest difficulties. It is testament to their tenacity that they remained. Growth, albeit tentative by international standards, has been sustained, at a fairly constant pace over the second half of the twentieth century, such that a critical mass of population has been sustained as has also their acceptance as part of Irish society.