This essay deals with the structure and organization of religion in Ireland in 1891, the year of Charles Stewart Parnell’s death. Using the replies to the questions on religion in the census of that year, it describes how the inhabitants of Ireland organized themselves for the worship of God in denominational groups. The evidence of the census is inherently problematic, however, since it recorded the confessional patterns of belonging in Ireland rather than the belief systems of its inhabitants. Thus, many of those recorded in the census as adherents to mainstream confessional groups had rather esoteric beliefs. This was certainly the case with Parnell, who although outwardly an orthodox Anglican actually held deist or pantheistic beliefs. For this reason, the essay explores marginal groups who attracted adherents because of their belief systems rather than for the social or political validation achieved through affiliation to mainstream religious denominations. Thus, the essay focuses on the Brethren, with whom Parnell has close family contacts; the Mormons; and the Christian Israelites, as well as on the beliefs and organization of a number of even smaller religious groups in Ireland.