Topics: is ireland made up mostly of catholics or protestants? know any good sites for info on ireland?
The Catholic Church in Ireland ( Irish : Eaglais Chaitliceach na hÉireann ) is part of the worldwide Catholic Church in communion with the Pope. With 3.7 million members, it is the most populous Christian denomination in Ireland , comprising 78.3% of the population. The Primate of All Ireland is the Archishop of Armagh and the Church ministers to Catholics on an All-Ireland basis; covering both the Republic of Ireland and Northern Ireland. The Irish Catholic Bishops' Conference is a consultative body for ordinaries in Ireland.
The Roman Empire never reached Ireland; so when the Edict of Milan in 313 AD allowed tolerance for the Levantine -originated religion of Christianity and then the Edict of Thessalonica in 380 AD enforced it as the state religion of the Empire; covering much of Europe (including Roman Britain ); the indigenous Indo-European pagan traditions of the Gaels in Ireland remained normative. Aside from this independence, Gaelic Ireland was a highly decentralised tribal society, so mass conversion to a new system would prove a drawn out process. 
The effect of the Act of Supremacy 1558 and the Papal bull of 1570 ( Regnans in Excelsis ) legislated that the majority population of both kingdoms to be governed by an Anglican Ascendancy. After the defeat of King James II of The Three Kingdoms in 1690, the Test Acts were introduced which began a long era of discrimination against the recusant Catholics of the Kingdoms.