Mangerton or Mangerton Mountain (Irish: An Mhangarta, meaning 'the long-haired (mountain)'), at 838 metres (2,749 ft), is the 19th-highest peak in Ireland on the Arderin list, and the 26th–highest mountain according to the Vandeleur-Lynam list. Mangerton is the tallest mountain in the Mangerton Mountain Group, also called the Mangerton Mountains or the Mountains of East Kerry, a range that includes five other major mountains that have a height above 2,000 feet (610 m). Mangerton's western slopes lie within the Killarney National Park. On Mangerton's north-western face lies a deep corrie lake called the Devil's Punchbowl, which is a popular scenic destination for hill walkers; although the mountain is often overlooked by walkers due to the proximity of its more scenic and accessible neighbour, Torc Mountain. The far northern slopes of Mangerton was the site of an important 13th-century battle between the Mac Cárthaigh (Gaelic forces), and the FitzGeralds (Norman forces), known as the "Tooreencormick battle site".

Irish academic Paul Tempan notes in the Irish Hill and Mountain Names database that Mangerton is most likely a translation of Irish: An Mhangarta, meaning "the long-haired". Tempan discussed the possibility that an alternative interpretation of Irish: An Mhangartach may be worth considering, as it could be the noun Irish: mangart with the suffix ach. Tempan notes P. S. Dinneen's Foclóir Gaedhilge agus Béarla—Irish-English Dictionary (1927), defines Irish: mangart as "movement" or "shaking". Thus the adjective (not listed in any dictionary) could mean "moving", "shaking", or "quaking", which could refer to the physical movement of Mangerton bog prevalent on the southern slopes, or could be understood figuratively as meaning "vacillating" or "fickle".

Mangerton's flat boggy summit plateau includes the satellite summits of Mangerton North Top 782 metres (2,566 ft) and Glencappul Top 700 metres (2,300 ft), and its "horseshoe-shaped" massif includes the summit of Stoompa 705 metres (2,313 ft). The Horses' Glen (or Glencappul), and the Devil's Punchbowl carve deep hollows, or corries on the north-west and north-east sides of Mangerton's massif, but the southern flanks form a huge plateau, one of the most extensive areas of mountain wilderness in Ireland, where herds of red deer and sika deer still roam.

There are three lochs that flow from Managerton's corries into the Horse's Glen (or Glencappul), namely the lowest, Lough Garagarry (Loch Garaigre), the middle, Lough Mannagh (Loch Meáin) and the Lough Erhogh, which is a hanging glacial lake set into a corrie on Mangerton's north-east face.

The Devil's Punchbowl (Irish: Poll Ifrinn), at 670 metres (2,200 ft) on Mangerton's north-west face is a deep oval-shaped corrie filled by a loch in its base that drains into the Owengarriff River from which Torc Waterfall is formed, before finally flowing into the Lakes of Killarney below. Mangerton's western slopes lie within the Killarney National Park.

Mangerton Mountain's height and topographic prominence, qualifies it to meet the British Isles Marilyn classification, as well as the Arderin, Simm and Hewitt classifications. Mangerton Mountain ranks as the 10th-highest mountain in Ireland on the MountainViews Online Database, 100 Highest Irish Mountains, where the prominence threshold is over 100 metres (e.g. higher mountains with sub-100-metre prominences are excluded).

Surrounding Mangerton are 25 other peaks with an elevation above 100 metres (330 ft) in a range known as the Mangerton Group (or Mangerton Mountains). The range is bounded by the "square" road system surrounding Mangerton, being the N71 to the north and the west side, the N22 to the east side, and the narrow R569 road from Kenmare to the N22 via Kilgarvan on the south side. Most notable are Dromderalough (650 metres (2,130 ft)), and its slightly higher Dromderalough North-East Top (654 metres (2,146 ft)), as well as Crohane (650 metres (2,130 ft)), and Knockbrack (610 metres (2,000 ft)). It also includes the tourist peak of Torc Mountain 535 metres (1,755 ft) in the north-west corner.

Mangerton's flat boggy summit plateau means that it can get overlooked when guidebooks of Ireland's best walks are compiled, particularly given its proximity to the rocky ridges and summits of the MacGillycuddy's Reeks; sometimes even nearby Torc Mountain is recommended instead. However, Mangerton's scale, summit views and deep corries are well regarded, and its proximity to Killarney town and ease of access are recognised by climbers.