Christianity is and has been the largest religion in
Ireland. Most Christian churches are organised on an all-Ireland basis, including both the
Republic of Ireland and
Northern Ireland. In the Republic of Ireland, 84.2% of the population adheres to the
Roman Catholic Church. In Northern Ireland, the various branches of
Protestantism collectively form a majority of the population but the single largest church is the Roman Catholic Church which accounts for some 40.8% of the population.