Fionn mac Cumhaill in the context of "Fenian Cycle"

King's Cave (Scottish Gaelic: Uamh an Rìgh) is the largest of a series of seafront caves north of Blackwaterfoot on the Isle of Arran in Scotland. The caves were formed around 10,000 to 6,000 years ago during an ice age when the weight of an advancing glacier forced the land downward, so the sea was higher relative to the location of the cave, with high tide around 4 metres (13 ft) up from its present level. When the ice melted, the land rose due to the isostatic rebound effect, thus forming a raised shoreline or raised beach with relict sea-cliffs. The hillside above the cliffs has a shallow slope resulting from a much earlier raised beach, nominally 30 metres (98 ft) above present high tide.

Kilmory Parish church records suggest the cave may have been used for church meetings in the eighteenth century, and it is also said to have been used as a school. Before being known as the King's Cave it was known as Fingal's Cave after Fionn mac Cumhaill, a figure in Irish mythology.

The Fenian Brotherhood (Irish: Bráithreachas na bhFíníní) was an Irish republican organisation founded in the United States in 1858 by John O'Mahony and Michael Doheny. It was a precursor to Clan na Gael, a sister organisation to the Irish Republican Brotherhood (IRB). Members were commonly known as "Fenians". O'Mahony, who was a Gaelic scholar, named his organisation after the Fianna, the legendary band of Irish warriors led by Fionn mac Cumhaill.

Irish mythology is the body of myths indigenous to the island of Ireland. It was originally passed down orally in the prehistoric era. In the early medieval era, myths were written down by Christian scribes, who Christianized them to some extent. Irish mythology is the best-preserved branch of Celtic mythology.

The myths are conventionally grouped into 'cycles'. The Mythological Cycle consists of tales and poems about the god-like Tuatha Dé Danann, who are based on Ireland's pagan deities, and other mythical races like the Fomorians. Important works in the cycle are the Lebor Gabála Érenn ("Book of Invasions"), a legendary history of Ireland, the Cath Maige Tuired ("Battle of Moytura"), and the Aided Chlainne Lir ("Children of Lir"). The Ulster Cycle consists of heroic legends relating to the Ulaid, the most important of which is the epic Táin Bó Cúailnge ("Cattle Raid of Cooley"). The Fenian Cycle focuses on the exploits of the mythical hero Finn and his warrior band the Fianna, including the lengthy Acallam na Senórach ("Tales of the Elders"). The Cycles of the Kings comprises legends about historical and semi-historical kings of Ireland (such as Buile Shuibhne, "The Madness of King Sweeny"), and tales about the origins of dynasties and peoples.

The king asleep in the mountain (D 1960.2 in Stith Thompson's motif-index) is a prominent folklore trope found in many folktales and legends. Thompson termed it as the Kyffhäuser type. Some other designations are king in the mountain, king under the mountain, sleeping hero, or Bergentrückung ("mountain rapture").

Examples include the legends of King Arthur, Fionn mac Cumhaill, Charlemagne, Ogier the Dane, King David, Frederick Barbarossa at Kyffhäuser, Falanto of Taranto, Genghis Khan, Constantine XI Palaiologos, Kraljević Marko, Sebastian of Portugal and King Matjaž.

Fianna (/ˈfiːənə/ FEE-ə-nə, Irish: [ˈfʲiən̪ˠə]; singular Fian; Scottish Gaelic: Fèinne [ˈfeːɲə]) were small warrior-hunter bands in Gaelic Ireland during the Iron Age and early Middle Ages. A fian was made up of freeborn young men and women, often from the Gaelic nobility of Ireland, "who had left fosterage but had not yet inherited the property needed to settle down as full landowning members of the túath". For most of the year they lived in the wild, hunting, cattle raiding other Irish clans, training, and fighting as mercenaries. Scholars believe the fian was a rite of passage into manhood, and have linked fianna with similar young warrior bands in other early European cultures.

They are featured in a body of Irish legends known as the 'Fianna Cycle' or 'Fenian Cycle', which focuses on the adventures and heroic deeds of the fian leader Fionn mac Cumhaill and his band. In later tales, the fianna are more often depicted as household troops of the High Kings.

Acallam na Senórach (Modern Irish: Agallamh na Seanórach, whose title in English has been given variously as Colloquy of the Ancients, Tales of the Elders of Ireland, The Dialogue of the Ancients of Ireland, etc.), is an important prosimetric Middle Irish narrative dating to c. 1200. It is the most important text of the Finn Cycle (also known as the Fenian Cycle, fíanaigecht, fiannaigheacht, fiannaíocht etc) and at about 8,000 lines is the longest-surviving work of medieval Irish literature. It contains many Finn Cycle narratives framed by a story in which the fianna warriors and Caílte mac Rónáin have survived long enough to relate the tales to Saint Patrick. The work has been seen as a defence of the Irish literary establishment when it came under the scrutiny of Church reformers during the 12th to 13th centuries.