Thank you for visiting. This article is the third installment in a series explaining the original texts of Celtic mythology.
This time, taking up Ireland’s “Fenian Cycle,” we look in detail at the story of the hero Fionn mac Cumhaill, who gained wisdom from the salmon of knowledge, and his warrior band, the Fianna.
For an overview map of Celtic mythology’s original texts as a whole, please see this summary article.
Let me organize in a diagram the place of the “Fenian Cycle” treated in this article and the Welsh “Mabinogion” treated next time (Article 4).
The main contents of the Fenian Cycle traced in this article are as follows.
| Story | Content |
|---|---|
| The salmon of knowledge | The boy Fionn gains omniscient wisdom |
| Slaying the goblin Aillen | Fionn becomes head of the Fianna |
| The deer-wife Sadhbh | A wife turned into a deer by magic, and the birth of his son Oisín |
| The Land of Eternal Youth | Oisín spends 300 years in the otherworld Tír na nÓg |
| Diarmuid and Gráinne | A fiancée’s elopement and Fionn’s merciless revenge |
| The Colloquy of the Old Men | A surviving warrior tells of the old days to Saint Patrick |
Fionn mac Cumhaill and the “Salmon of Knowledge”
The “Fenian Cycle” is a body of stories depicting the adventures of the hero “Fionn mac Cumhaill” and the warrior band “Fianna” he leads. If the previous Cú Chulainn is “a tragic young hero,” Fionn is depicted as a mature hero skilled in wisdom and leadership.
What tells of the source of Fionn’s wisdom is the famous tale of the “salmon of knowledge.”
As a boy, Fionn was studying under the poet “Finegas.” Finegas, over seven years, finally caught the “salmon of knowledge,” said to “grant whoever eats it all the knowledge of the world.” He ordered Fionn to cook that salmon and warned him, “You must never eat it.”
But while cooking the salmon, Fionn burned his thumb on the spitting fat and unthinkingly put that thumb in his mouth. Thus the first to gain the power of the salmon of knowledge was not Finegas but Fionn. From then on, Fionn could see all knowledge and the future by biting his thumb.
Celtic Myth: Goddesses, Heroes and FairiesView on Amazon →
An Illustrated Guide to Celtic MythologyView on Amazon →
Slaying the Goblin Aillen and Becoming Head of the Fianna
What tells how Fionn became head of the warrior band Fianna is the story of “Aillen, the goblin who burns Tara.”
At the time, the royal court Tara was tormented each year, on the night of the “festival of Samhain (All Hallows),” by a goblin of the fairy folk, “Aillen.” Aillen would lull people to sleep with the beautiful sound of his harp, and once all were asleep, breathe fire from his mouth and burn down the court of Tara. This had continued for 23 years, and not one person could prevent it.
There the young Fionn appeared, pressed the point of a magic spear to his own forehead, and overcame his drowsiness by its pain and killing intent. Then, unbeguiled by the lulling melody, he slew Aillen as he tried to breathe fire. As a reward for removing this long-standing threat, Fionn was appointed head of the warrior band Fianna.
Joining the Fianna required superhuman trials. For example, buried up to the waist in the ground, to defend with only a shield against spears nine men throw at once; to run through a forest without disturbing a single hair or breaking a single branch; to pull a thorn from one’s foot while running — all said to be impossible for ordinary people.
Fionn’s Hounds, and His Wife Sadhbh, Who Became a Deer
Fionn had two wise hounds, “Bran” and “Sceólang,” who understood human speech. In fact these two had the origin of being human nephews turned into dogs by magic.
Concerning these hounds is the story of Fionn’s wife “Sadhbh.” Sadhbh had been turned into a “doe” by the magic of a fairy whose courtship she had refused. Once, toward a doe Fionn was about to bring down in a hunt, the hounds Bran and Sceólang somehow did not attack but nuzzled it gently. When Fionn brought the deer home, it returned to the form of a beautiful woman, Sadhbh.
The two are united, but during Fionn’s absence, Sadhbh is again turned into a deer by fairy magic and carried off. Later Fionn took in a feral child found in the forest. It was the son Sadhbh bore in deer form, and he is named “Oisín (little deer).” This Oisín is the very poet-warrior who crosses to the Land of Eternal Youth, told of next.
Oisín, Who Crossed to the Land of Eternal Youth
A poignant story is handed down of Fionn’s son, the poet-warrior “Oisín.”
Oisín is taken with by the fairy-land princess “Niamh” and crosses to the paradise across the sea, “Tír na nÓg (the Land of Eternal Youth).” It was an ideal land without aging or death, and Oisín spent happy days there.
Eventually growing homesick, Oisín is permitted to return temporarily, but is warned, “Never set your foot on the ground.” But returning home, Oisín learns that three years in the Land of Eternal Youth were 300 years on earth. His father Fionn and the Fianna were long beyond into legend.
And, in the act of trying to help the people of the earth, Oisín accidentally falls from his horse and touches the ground. In that instant, he was utterly transformed into an old man of 300 years all at once. A Celtic-style story depicting the tragedy of an otherworld with a different flow of time and the human world.
The Tragic Love of Diarmuid and Gráinne
The Fenian Cycle also has the tragic love story of “Diarmuid and Gráinne.”
The aged Fionn tries to take the young, beautiful princess “Gráinne” as his wife. But Gráinne falls in love with Fionn’s trusted young warrior “Diarmuid” and the two elope.
Fionn pursues the two persistently but, after long years, is once reconciled. Yet later, during a hunt, Fionn finds Diarmuid, gored near death by a wounded boar. Fionn had the power that “if he gives water scooped in both hands, he can save a life,” but out of his old grudge he deliberately spilled the water and let Diarmuid die. This story is said to have influenced the later tragic love of Tristan and Isolde.
How the Fenian Tales Were Handed Down — Oisín and Saint Patrick
The very “frame” by which the Fenian Cycle was handed down is fascinating too. In the representative medieval original text the “Colloquy of the Old Men (Acallam na Senórach),” the story proceeds in the form of the old Oisín (or the likewise long-lived Caílte), who returned from the Land of Eternal Youth and survived 300 years, meeting and conversing with Saint Patrick, who came to bring Christianity.
The aged pagan warrior Oisín nostalgically tells of the glory of the heroes gone by — the joy of the hunt, the pride of the Fianna, the lavish feasts — and Saint Patrick has it written down. This structure, in which the old pagan heroic world faces the new Christian world, tells well that Celtic myth was handed down with “a longing for the perishing good old days.”
And of Fionn himself, the legend remains that he did not die but sleeps in a cave, and when Ireland falls into true crisis, he will revive with the sound of a horn and save the land. This much resembles the “once and future king” legend of Britain’s King Arthur, showing the “sleeping hero” theme common to the Celtic world.
To Learn More
Here are some related books. Reading them alongside this series lets you savor this world even more deeply.
Celtic Myths and LegendsView on Amazon →
European Iconography: Myths, Legends and Fairy TalesView on Amazon →
Conclusion
In this article, I explained Ireland’s Fenian Cycle in detail, following the original texts. How was it?
“Fionn mac Cumhaill,” who gained omniscience from the salmon of knowledge; his wife Sadhbh, who became a deer; “Oisín,” who returned aged from the Land of Eternal Youth; and the tragic love of Diarmuid and Gráinne — I hope you could savor a Celtic world of warrior bands, hunts, and melancholy, different from both the age of the gods (Article 1) and the hero Cú Chulainn (Article 2).
In the next article (Article 4, the finale), I will explain Celtic mythology’s other treasury, the Welsh myth collection the Mabinogion. There lies a source of the Arthurian legends.
With this, the (three-article) series on Celtic mythology’s original texts continues. I hope you have enjoyed the world of Celtic mythology, from the battles of the gods to the adventures of the heroes.
For the big picture of Celtic mythology’s original texts and the list of other myths and religions, please see the pages below.
I hope you’ll read the next article too.
📚 Series: The Original Texts of Celtic Mythology (4/5)
