Ireland doesn't have an official national animal as such, as in Ireland such symbols are often defined by common usage rather than by official acts, in part because many of them pre-date the relatively recent partition of the island.
Ireland's national animal
However, an oft-cited national animal of Ireland is the Irish hare, known outside of Ireland as the mountain hare. Irish hares are the only lagomorphs (the group containing hares, rabbits, and pikas) native to the island of Ireland and are thought to have been there for at least a couple of million years, with fossils found dating back to the late Pleistocene.
Although much larger than rabbits they are similarly often russet brown in colour with a white tail. As a group, mountain hares tend to moult to white in the winter, but the Irish population of the species rarely does.
The Irish hare is widespread throughout Ireland, from its coastal dunes to mountain tops, moorland to rolling fields.
Main image: Irish hare illustration © from "British Mammals" by A. Thorburn, 1920. Public domain, via Wikimedia Commons