The vast majority of placenames in Ireland are anglicisations of Irish language names; that is, adaptations of the Irish names to English phonology and spelling. However, some names come directly from the English language, and a handful come from Old Norse and Scots. The study of placenames in Ireland unveils features of the country's history and geography and the development of the Irish language. The name of Ireland itself comes from the Irish name Éire, added to the Germanic word land. In mythology, Éire was an Irish goddess of the land and of sovereignty.

Ulster is one of the four traditional or historic Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland ; the remaining three are in the Republic of Ireland.