The digitized Irish Catholic Parish Registers, 1740s - 1880s are now free online. The National Library of Ireland has placed 390,000 images from more than 1,000 Catholic Perishes online. You will find them at registers.nlie.ie. The records are not indexed. You must browse to find the record you need. You still need to know where in Ireland the birth, or marriage occured to find your ancestor's church baptism or marriage record.