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 (e.g. the change in elevation required between neighbouring mountains), 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 lowest minimum prominence threshold of any definition of an Irish mountain is 15 metres (49 ft) (e.g. the Vandeleur-Lynam), however most definitions, including the International Climbing and Mountaineering Federation (UIAA) criteria, do not consider prominences below 30 metres (98 ft) as being mountains (e.g. must at least be an Arderin or a Hewitt). Many British definitions consider a peak with a prominence below 150 metres (492 ft), as being a top, and not a mountain (e.g. must be a Marilyn). A widely used definition of an Irish mountain requires a minimum prominence of 100 metres (328 ft) (e.g. a HuMP), and is the basis for the 100 Highest Irish Mountains.
While Irish mountains are ranked according to Irish classifications, they are also ranked on classifications that cover Britain and Ireland (e.g. Simms and P600s).
There is no consensus on the definition of "mountain", but in Britain and Ireland it is often taken to be a summit over 2,000 ft, or more latterly, 600 m. There is less consensus about the topographical prominence requirement (e.g. the change in elevation required between neighbouring mountains), which can vary between 30–150 m (98–492 ft). Prominence is even strongly debated regarding UIAA classification of Himalayan mountains. In the alps, the UIAA requires a prominence of over 30 m to be a "peak" and over 300 m to be a "mountain".
The lowest threshold of prominence in Britain and Ireland is 15 metres (49 ft). The only definition in which prominence is not used, is where topographic isolation is used (e.g. the use of "sufficient separation" for Munros). Most Britain and Ireland definitions no longer categorise prominences below 30 metres (98 ft) (e.g. no new Nuttalls and Vandeleur-Lynams), and peaks with a prominence between 30–150 metres (98–492 ft) are now defined as tops rather than mountains (e.g. the 227 Munro Tops).
In Ireland, a prominence threshold of 100 metres (328 ft) is proposed for a mountain.
The term Dillon is used to describe any of the 212 Irish summits in Paddy Dillon's well–regarded Irish 2010 climbing guidebook: "The Mountains of Ireland". All of Dillon's summits are over 2,000 ft (610 m), and almost all have a prominence above 30 m (98 ft) (i.e. they are very similar to the list of 209 Irish Hewitts).
The term Myrddyn Deweys are peaks in Ireland, between 500 metres to 2,000 feet (609.6 metres) in height, with a prominence above 30 metres (98 feet), which was published by Michael Dewey and Myrddyn Phillips in 2000. Myrddyn Deweys are the Irish equivalent of Deweys, which extend the Hewitt classification down to 500 metres. There are 200 Myrddyn Deweys.
MountainViews was created in 2002 by Simon Stewart as a non–profit online database for climbers in Ireland to document and catalogue their Irish climbs. Its main data source are from the Ordnance Survey Ireland (OSI) maps, although it also conducts its own surveys, which the OSI has integrated into its own database, and it also integrates other important Irish mountain databases such as the Paul Tempan's work with the Placenames Database of Ireland (Loganim). Collins Press published the MountainView Online Datase in 2013 in the book: A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arderins.
Since 2012, MountainViews has been partnered with the Database of British and Irish Hills (DoBIH), which is the main live database for the categorisation of mountains and hills in Britain and Ireland. However, MountainViews can differ slightly from DoBIH on the measurements for certain Irish mountains.
The MacGillycuddy's Reeks range contains Ireland's highest mountain, Carrauntoohil 1,038.6 m (3,407 ft), and the Reeks is the highest range of peaks in Ireland. However, many of its peaks do not meet all classification criteria for a "mountain" (e.g. particularly the 100–150 m (330–490 ft) in elevation change from neighbouring mountains), and many are not in the 100 Highest Irish Mountains. Regardless, the range contains ten of the thirteen Scottish Furths in Ireland, and given its importance, and as an important example of complexity of mountain classification, the ten highest Reeks are listed below:
(any height, prominence over 100 m)
This is the MountainViews 100 Highest Irish Mountains list, which was published by Collins Press in the 2013 book: A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arderins. It combines Paul Tempan's 2012 research into Irish mountains and Irish mountain names. The list requires a prominence of over 100 m (328 ft), a compromise between the popular British Isles Marilyn criteria of 150 metres (see List of Marilyns in the British Isles for a ranking of Irish Marilyns by height and by prominence), and the Simms–Hewitt–Arderins criteria of 30 metres (see List of mountains of the British Isles by height for a ranking of Irish Simms by height and by prominence). It is a widely used list, and it contains 25 of the 26 Irish P600s (Slieve Snaght, a P600, did not make the 100 Highest).
(height above 500 m, prominence over 30 m)
A noted definition of an Irish mountain over the lower height threshold of 500 m (1,640 ft), is the Arderins list, but which meets the minimum requirement for a "mountain" with a prominence above 30 m (98 ft), and is an Irish equivalent of the Hewitt (the 207 Arderins over 2,000 ft (610 m) are the 207–209 Irish Hewitts), or the Simm (the 222 Arderins over 600 m (1,969 ft) are the 222–224 Irish Simms). The 199 Arderins below 2,000 ft (610 m) are the Myrddyn Deweys (e.g. the total of the 207 Irish Hewitts and the 199 Myrddyn Deweys equal the 406 Irish Arderins).
MountainView's Online Database of Arderins was published by Collins Press in the 2013 book: A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arderins, and updated in 2015. In 2023, the MountainView Online Database listed 409 Irish mountains as meeting the Arderin definition. Several of the MountainViews.ie users have recorded completing the entire list of Arderins. One user having completed the Arderins within one single year (2014) along with the complete list of Vandeleur-Lynams, county highpoints and the highest 100 list.
MountainViews uses the term Arderin Begs for the additional class of peaks over 500 m (1,640 ft) in height, and with a prominence between 15–30 m (49–98 ft). In 2018, Ireland had 124 Arderin Begs.
(height above 600 m, prominence over 15 m)
The broadest noted definition of an Irish mountain over 600 m (1,969 ft) is the Vandeleur-Lynam list, as it only requires a prominence of 15 m (49 ft), and is the Irish fully metric equivalent of the England & Wales Nuttall. The 100 Highest Irish Mountains from above, is a subset of this list (e.g. they are all Vandeleur-Lynams). For example, Mweelrea, the highest mountain in Connacht, is 16th on the 100 Highest Irish Mountains list, but 34th on the Vandeleur-Lynam list. MountainView's Online Database of Vandeleur-Lynams was published by Collins Press in the 2013 book: A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arderins, and updated in 2015. In 2023, the MountainView Online Database lists 275 Irish mountains as meeting the Vandeleur-Lynam definition.
On 3 October 2018, English Lake District climber, James Forrest, completed all 273 Irish Vandeleur-Lynams in 8 weeks. In 2023, Irish photographer and adventurer Ellie Berry completed the Vandeleur-Lynams, now 275 peaks, in 50 days and 5 hours beating the previous record by 6 days.
MountainViews and Database of British and Irish Hills recognise a list of 337 summits as Carns, having height above 100 m (328 ft) and below 400 m (1,312 ft).
MountainViews and Database of British and Irish Hills recognise a list of 484 summits as Binnions, having prominence at least 100 m (328 ft) and height below 400 m (1,312 ft).
There are 4 Irish Provincial Tops, namely: Carrauntoohil, in Munster, Lugnaquilla in Leinster, Slieve Donard, in Ulster, and Mweelrea in Connacht.
In addition, there are 27 Irish County Tops, as 10 counties share the same county top, namely: Galtymore for Limerick/Tipperary, Mount Leinster for Carlow/Wexford, Sawel for Londonderry/Tyrone, Cuilcagh for Cavan/Fermanagh, Arderin for Laois/Offaly.
Whereas the MountainViews, Vandeleur-Lynam, and Arderin classifications are unique to Ireland, Irish mountains appear in other similar classifications that have been used in across Britain and Ireland.
The Britain and Ireland Simms classification (height over 600 m, and prominence above 30 m), is very similar to the Irish Arderin classification (height over 500 m, and prominence over 30 m). As of October 2018, the 2,754 Simms in Britain and Ireland, which include 224 Irish Simms (i.e. the Irish Arderins over 600 m), are ranked by height, and by prominence, on this table:
Irish Hewitts, which have largely been replaced by the metric Simms classification, are ranked against English and Welsh Hewitts on these tables:
The popular Britain and Ireland Marilyn classification (any height, and prominence above 150 m), is a more severe prominence threshold than the Irish Mountainviews classification (height over 500 m, and prominence over 100 m). As of October 2018, the 2,011 Marilyns in Britain and Ireland, which include 454 Irish Marilyns (e.g. the amount is larger because Marilyns will take any height, as long as the peak meets the prominence threshold), are ranked by prominence, and by height, here (note that this list is commonly used to rank by prominence, as it includes any peak with prominence above 150 m):
The Britain and Ireland P600 classification require a prominence above 600 m (e.g. and by definition, the height must, therefore, be above 600 m), and are thus called the "Majors". As of October 2018, the 120 P600s in Britain and Ireland, which include 26 Irish P600s, are ranked by height here:
Finally, the Scottish Furth classification is for mountains that the Scottish Mountaineering Club ("SMC") identify as meeting the classification for a Scottish Munro, however, they are outside (e.g. they are "furth") of Scotland. As of October 2018, the 34 Furths in Britain and Ireland, which includes 13 Irish Furths, are ranked by height here:
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