In these lists of mountains in Ireland, those within Northern Ireland, or on the Republic of Ireland – United Kingdom border, are marked with an asterisk, while the rest are within the Republic of Ireland. Where mountains are ranked by height, the definition of the topographical prominence used to classify the mountain, is noted. In British definitions, a height of 600 metres (1,969 ft) is required for a mountain, whereas in Ireland, a lower threshold of 500 metres (1,640 ft) is sometimes advocated.

The mountains and hills of the British Isles are categorised into various lists based on different combinations of elevation, prominence, and other criteria such as isolation. These lists are used for peak bagging, whereby hillwalkers attempt to reach all the summits on a given list, the oldest being the 282 Munros in Scotland, created in 1891.