If you are looking for historical Church Register records please first check the Diocesan guidelines link for researching family history. This will help you in the process and explain what a parish can and cannot provide. ("Guidelines" Button).
You should also first search the "useful links" below.
This website contains images from the NLI’s collection of Catholic parish register microfilms. The registers contain records of baptisms and marriages from the majority of Catholic parishes in Ireland and Northern Ireland up to 1880.