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 is required for a mountain, whereas in Ireland, a lower threshold of is sometimes advocated.
The lowest minimum prominence threshold of any definition of an Irish mountain is (e.g. the Vandeleur-Lynam), however most definitions, including the International Climbing and Mountaineering Federation (UIAA) criteria, do not consider prominences below as being mountains (e.g. must at least be an Arderin or a Hewitt). Many British definitions consider a peak with a prominence below , 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 (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 Great Britain and Ireland (e.g. Simms and P600s).
Definitions
General concepts
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.Wilson, Peter (2001). Listing the Irish hills and mountains in Irish Geography, Vol 34(1), University of Ulster, Coleraine, p. 89. (pdf) There is less consensus about the topographical prominence requirement (e.g. the change in elevation required between neighbouring mountains), which can vary between . 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 . 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 (e.g. no new Nuttalls and Vandeleur-Lynams), and peaks with a prominence between are now defined as tops rather than mountains (e.g. the 227 Munro Tops).
In Ireland, a prominence threshold of is proposed for a mountain.
Main classifications
Other classifications
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 , and almost all have a prominence above (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 in height, with a prominence above , 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 Online Database
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.
List of the 10 Highest MacGillycuddy's Reeks
The MacGillycuddy's Reeks range contains Ireland's highest mountain, Carrauntoohil , 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 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:
The 10 highest peaks of the MacGillycuddy's Reeks, regardless of prominence (MountainViews Online Database, October 2018)RankIrish nameOther namesHeightProminenceListedNot Listed1Corrán TuathailCarrauntoohil Real Munro, Furth, P600, Marilyn, Hewitt, Simm, Vandeleur-Lynam, Arderin, MountainViews —2Binn ChaorachBeenkeragh, Benkeeragh Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews3Cathair na FéinneCaher, Caher East TopFurth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews4Cnoc na PéisteKnocknapeasta Real Munro, Furth, Marilyn, Hewitt, Simm, Vandeleur-Lynam, Arderin, MountainViews P600 5Cathair ThiarCaher West Top Furth, Vandeleur-Lynam Real Munro, P600, Marilyn, Hewitt, Simm, Arderin, MountainViews6Maolán Buí— Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews7Cnoc an Chuillinn— Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews8Na CnámhaCarrauntoohil Tooth, The Bones, Knockoughter Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews9An Gunna MórThe Big Gun Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews10Cruach Mhór— Furth, Hewitt, Simm, Vandeleur-Lynam, Arderin Real Munro, P600, Marilyn, MountainViews
100 Highest Irish Mountains
(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 , 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).