The Catholic Church in Ireland is part of the worldwide Catholic Church, under the spiritual leadership of the Pope and curia in Rome. There are an estimated 4.5 million baptised Catholics in Ireland out of a total population of just under 6 million.
The Church is organised into four provinces, not however, corresponding with the provincial divisions. It is ruled by four archbishops and twenty-three bishops. But the number of dioceses is more than twenty-seven, there have been amalgamations and absorptions. Cashel, for instance, has been joined with Emly, Waterford with Lismore, Ardagh with Clonmacnoise, the bishop of Galway being also Apostolic Administrator of Kilfenora. The number of parishes is 1,087, a few of these are governed by administrators, the remainder by parish priests, while the total number of the secular clergy—parish priests, administrators, curates, chaplains, and professors in colleges—amounts to around 3,000. A full list of dioceses can be found here: List of the Roman Catholic dioceses of Ireland.
There are also many religious orders which include: Augustinians, Capuchins, Carmelites, Fathers of the Holy Ghost, Dominicans, Franciscans, Jesuits, Marists, Order of Charity, Oblates, Passionists, Redemptorists, and Vincentians. The total number of the regular clergy is about 700. They are engaged either in teaching or in giving missions, but not charged with the government of parishes.
In addition there are two societies of priests founded in Ireland, namely St Patrick's Missionary Society with its headquarters in County Wicklow and the Missionary Society of St. Columban who are based in County Meath.

History, legal status and politics
Brentwood · Norwich · Northampton · Nottingham · Westminster
Birmingham · Clifton · Shrewsbury
Lancaster · Leeds · Liverpool · Middlesbrough · Newcastle-upon-Tyne · Salford · Sheffield
Arundel · Plymouth · Portsmouth · Southwark
Cardiff · Swansea · Wrexham
Bishopric of the Forces · Apostolic Exarchate for Ukrainians
Aberdeen · Ayr · Dumfries · Dundee · Edinburgh · Oban
Glasgow · Motherwell · Paisley
Armagh · Belfast · Cavan · Derry · Letterkenny · Longford · Monaghan · Mullingar · Newry
Cobh · Cork · Ennis · Killarney · Limerick · Skibbereen · Thurles · Waterford
Carlow · Dublin · Enniscorthy · Kilkenny
Ballaghaderreen · Ballina · Galway · Loughrea · Sligo · Tuam

Roman Catholicism by country
Apostolic Nuncio to Ireland