Fionn mac Cumhail (Finn Mac Cool) was the central figure of the Fenian Cycle, sometimes called the Ossianic Cycle after Fionn’s son Oisin. Fionn was leader of the Fianna or Fenians, said to have been bodyguards of the Irish high king beginning from c. 300 B.C.E. Some have suggested that the tradition of the Fenians influenced the myths of King Arthur and the fellowship of the Round Table. The source material for the Fenian tales probably dates back to the third century C.E., based on the tellings of the filidh. But the tales as we know them were written down in the twelfth-century Acallamh na Senorach (“The Colloquy of the Ancients”) by Christian monks, the influence of whose religion is apparent in the myths. The narrator of the Acallamh, Cailte, or sometimes Oisin (thus, Ossianic Cycle), for instance, recounts the Fenian adventures to Saint Patrick.

Named Demna by his druidic parents, the boy hero was so fair that he was renamed Fionn. The druid Finegas gave Fionn the Salmon of Knowledge to cook. The boy burned a finger in the process and, naturally enough, sucked on it to relieve the pain. In so doing he acquired the Salmon’s knowledge. In much the same way the Norse hero Sigurd gained certain powers when he sucked on a finger burned while roasting a dragon’s heart.

After a series of adventures, Fionn saved the high king, Cormac Mac Art, and was made leader of the Fianna. In a battle known as the Battle of Fionn’s Strand, Fionn overcame the mysterious “King of the World.” By the goddess Sadb, he fathered Oisin. It seems that Fionn had seen a fawn while hunting and that at night the fawn had become, for a brief time, human and female and had become Fionn’s lover. It was the “Dark Druid” who had turned Sadb into a fawn. Later, while looking for Sadb near Ben Bulben, Fionn found a naked fawn boy; this was his son Oisin.

Oisin, too, became a great hero, even taking a journey into the Underworld, where he stayed for three hundred years. It is upon his return that he tells the Fenian tales to Saint Patrick.

It is thought that one day Fionn will return to save Ireland, a “once and future king,” like King Arthur.