You already know, of course, that you can’t really trace your ancestry back to Niall of the Nine Hostages, or to anyone grand and legendary like that. And you probably also suspect, if your family tree looks anything like mine, that traditional family lore along the lines of ‘We were once the kings and queens of Ireland!’ rests on dubious and shaky grounds at best; and turns out to be, upon further investigation, something more like, ‘We were once the agrarian underclass of the counties of Cork and Tipperary!’
So: how far back can you really, and realistically, go?
Well, if you want to leave the lovely mists of time to legend and folklore and cheesy Celtic-centred romance novels (where the prototypical hero seems more Scottish than Irish, I guess, and that lusty Highlander on the book cover looks like nobody who was ever cleared off his land in a forced emigration scheme to Cape Breton, by the way…), and want to only ground your family history in actually surviving/extant records and documents: not very far at all, really, comparatively speaking (by comparison with, say, French Canada, where it’s possible to trace even very humble folk back to 16th- and 17th-century France). It’s great to see more and more Irish records go online, but let’s be honest here: those records have some pretty serious practical and temporal limitations.
You should be able to trace any Irish Catholic family back to 1850 or so, with a bit of luck and a great deal of perseverance.
But pre-1850, it gets a bit trickier, and much more contingent upon the survival of certain types of records (church records; military records; land records; records of immigration; and so on). This blog seeks to avoid needless controversy, wherever possible (because we’re Canadian, and therefore committed to reasonable compromise, and so on and so forth, and all of that boring stuff); but it has to be said that the Famine was a social trauma that left its mark on, amongst other effects, that area that is now known as “the genealogical record”: there are some sorts of documents that one might reasonably expect to uncover in a 19th-century, western, anglo-centred entity, but which simply do not exist for Ireland, because of the peculiarities of its colonial governance and the concomitant socio-economic upheavals attendant upon that rule; and that the Penal Laws also contributed to the (now so frustrating for genealogists) non-existence of some RC records, too.
If you can trace an Irish RC family back to about 1800 or so, you should consider yourself lucky (and perhaps unusually skilled as a researcher, or unusually perseverant).
Back to 1700 you almost certainly cannot credibly go; and anything further back than that gets us into the realm of mythology, or of cheesy Celtic-centred romance novels with lusty Highlanders (so: more Scottish than Irish, as mentioned above) wearing rough tartans and bearing broadswords on the cover.