Folklore Friday: The Four Cycles of Irish Mythology

Folklore Friday: The Four Cycles of Irish Mythology

Posted by Olivia O'Mahony on 21st Jun 2019

To put it plainly, the mythology of Ireland is comparable to a large, colorful Celtic knot — that is, beautiful, overflowing with meaning, and very often nigh-impossible to untangle. Timelines blur; facts seem to flip; characters that seemed to have a concrete home in one story dart like white rabbits through the corners of others. It’s enough to overwhelm even the most avid lover of folklore, no matter how determined they are to clarify the big picture of Irish legend — and that’s exactly why at Shamrock Craic have taken it upon ourselves to break it all down for you.

Here, we’ve got all of the information you need to get filled in on the four primary cycles of Irish mythology, the better to understand their eras, themes, conventions, main characters, and more. So settle in, and allow yourself to escape into the realm of the fantastic. It’s time to get mythical.


In terms of its stories’ temporal settings, the Mythological Cycle is the oldest division of Irish lore. It concerns itself with accounts of the “godlike figures” who arrived in Ireland while the island was still new to the world.

Many of these characters were members of the Tuatha Dé Danann, a supernatural race who represented the primary deities of pre-Christian Gaelic Ireland. Later, as Christian values and belief systems began to take hold, they be more often referred to as the Aos Sí (or fairy folk) of old Irish lore, with some believers even considering this transformation to be literal rather than merely ideological.

While active, Tuatha Dé Danann are said to have ruled over all of Ireland before mortal people (or the Milesians, the name often given to the final race to settle there) ever set foot on its soil. Because of this, happenings in their stories are often untethered to any markedly human sense of logic: in the story of Tochmarc Étaíne, or “The Wooing of Étaín,” the title character is turned into a fly, only to be swallowed by noblewoman who becomes pregnant and delivers her as a baby girl.

As the time of the Tuatha Dé Danann’s reign in Ireland came to an end, it’s said that they retreated beneath the fairy mounds that dotted the island’s landscape. However, being immortal, they did not die, and so often made surprise “guest appearances” in stories from other cycles. For example, Aengus (a being associated with love, youth, and inspiration) came to the aid of Echaid and Ébliu, a pair of young lovers in the Ulster Cycle, just as it appeared that their attempt to elope had been thwarted. Kindly, he gifted them hem with a supernaturally-large horse on which they could escape the province of Munster together.

When thinking about the Mythological Cycle, it’s important to remember that its characters are not to be considered gods outright, but merely “godlike” in their appearance, conduct, and doings; this distinction exists, however, due to the prudence of the Christian scribes who penned the cycle’s stories. Due to their relatively-new faith, they were reluctant to allow the undeniably pagan figures divine status, even on paper. Even still, the figures’ ties to the early Irish polytheistic worldview are quite thinly-veiled, and this provides ample explanation for the strange and wonderful happenings in the stories associated with this mythic cycle.


The Ulster Cycle is primarily composed of the best-known stories that take place before or around the first century A.D., the time of the birth of Jesus Christ. Previously, it was referred to as the Red Branch Cycle, after the royal houses of the King of Ulster, Conchobar Mac Nessa, who features prominently in its accounts. Interestingly, King Conchobar’s birth and death dates are said to have aligned exactly with those of Jesus Christ, though these are likely revisionist elements added by the Christian scribes who translated oral tradition into written text.

Unlike much early Irish literature, which illustrates Ireland as a placed unified under a series of different High Kings, the Ulster Cycle depicts a country with no overall ruling authority; rather, it is divided into many regional kingdoms, with many of the most well-known stories concerning the wars they fight against each other. Wealth was measured by the number and quality of the cattle that one owned (this will become important in a moment), and warfare was waged in one of two ways: cattle raid assaults, or one-to-one combat between a selected pair of champions.

King Conchobar ruled over eastern Ulster and northern Leinster, which at the time comprised a region known as the Ulaid. He was also the uncle of Cú Chulainn, the legendary hero and most important character of the cycle, and the nemesis of Medb, the warrior queen of a group of ancient dynasties known as the Connachta.

The most important story of the Ulster Cycle concerns this conflicted relationship, and is called the Táin Bó Cúailnge, or “Cattle Raid of Cooley.” In the legend, Queen Medb and her husband Ailill plot to steal the donn cuailnge, an Ulster brown stud bull said to be the most fertile in all of Ireland. The Queen raises an army to march on the province and take the animal by force, but they are met by a seventeen-year-old Cú Chulainn, who challenges Medb’s men to fight him in single combat. In a battle that lasts for months, Cú Chulainn systematically defeats champion after champion — but all the while, members of the Connachta are tracking down the donn cuailnge and driving it into their territory. When they arrive, the brown bull is pitted in a fight to the death against Medb’s own prize stud to prove its power; it wins, but ultimately succumbs to its injuries and dies.

Another essential reading segment from the Ulster Cycle is the tragedy of Deirdre, or “Deirdre of the Sorrows.” Upon her birth, it was prophesied that Deidre would grow up to be a young woman of extraordinary beauty, and upon hearing this, King Conchobar swore that when she was to become his bride when she reached a suitable age. However, once blossomed into a lovely young woman, Deidre fell in love with Naoise, a handsome young warrior of Conchobar’s court. Together, they fled to Scotland, and for a time lived happily; however, before long, they were tracked down by the humiliated and furious king. The two went into hiding, taking up lodging at the Red Branch house in Co. Armagh, but were found again. This time, Naoise was killed.

After the death of her beloved, Deirdre was captured and forced to marry Conchobar, though the spite she felt towards him only grew over time. Frustrated with his unhappy marriage, the king planned to give Deirdre away to the man whose spear had slain Naoise. This was too much for the young woman to bear. Upon hearing of Conchobar’s plan for her, Deidre jumped from the chariot in which they rode, finally joining her true love in the embrace of oblivion.


The Fenian Cycle of Irish mythology goes by many additional names, including the Finn Cycle and the Ossianic Cycle; the latter being after its primary narrator, Oisín, a warrior of the Fianna and the greatest poet of Irish mythohistory.

Fittingly, each story of the Fenian Cycle relates to the trials and accomplishments of the members of the Fianna and Fionn Mac Cumhaill, the group’s leader and Oisín’s father. Chronologically, it takes place after the Ulster Cycle and before the Cycle of the Kings, and differs from both in that it deals primarily with bands of heroes and hunters rather than figures of royalty. In this regard, its narratives are often compared to those of the Knights of the Round Table in British myth.

Most of the relevant poems and texts of the Fenian Cycle were penned between the seventh and fourteenth centuries. Interestingly, when one is asked to think about Irish mythology as a whole, often the first stories that spring to mind are those which stem from the Fenian Cycle. One of these is the Salmon of Knowledge, part of a greater narrative titled The Boyhood Deeds of Fionn, in which young Fionn eats the flesh of the wisdom-granting fish and so gains the knowledge of the world. This brilliance is how Fionn rose to eventually become the leader of the Fianna, Ireland’s greatest band of heroes and poets.

Another staple story of the Fenian Cycle is that of Oisín in Tír na nÓg. This cautionary tale tells of how Oisín meets Niamh, a princess of Tír na nÓg, a land across the sea whose denizens would forever remain young, beautiful, and carefree. The pair fall in love, and Oisín is persuaded by Niamh to come and live with her in her homeland. After three happy years together, however, Oisín grows homesick, and wishes to travel home to visit his father, Fionn. Niamh agrees to let him go, but there is one condition Oisín must obey: he must ride back to Ireland over the sea on her horse, and must never let his feet touch the ground.

Upon returning to Ireland, Oisín is shocked to discover that not three years have passed, like in Tír na nÓg, but 300. He is devastated to learn that his father and Fianna warrior brothers are long dead, and, in his grief, falls from the back of Niamh’s horse and onto the ground. Immediately, Oisín ages over 300 years, and dies of old age, never to be reunited with Niamh.


The Cycle of the Kings, otherwise known as the Historical Cycle, is the name given to the stories of the kings of Gaelic Ireland. In these stories, Ireland itself is frequently evoked as a goddess that the ruler of the tale in question might marry. This is because, at the time, the prosperity of the realm was seen as closely connected to the strength and wisdom of the king that oversaw it.

The Cycle of the Kings includes accounts of many semi-historical Irish rulers who illustrate different elements of kingship (both good and bad) through their choices and actions. One such example is Cormac Mac Airt, who was so wise and level-headed that Manannan, the ancient Irish sea deity, entrusted him with a goblet which broken into thirds when a lie was spoken, and came back together when the truth was revealed. Another was Labhraidh Loingseach, who overcame his self-inflicted inability to speak in order to take his rightful place as king from a cruel and unjust relative.

A common recurring theme in the Cycle of the Kings is that of the geasa, or a magical vow of either prohibition or obligation. The geasa can take the form of both a curse and a blessing, though if the one who has undertaken it should violate its terms, they risk great dishonor or even death. On the other hand, abiding by the rules of one’s geasa is believed to bring one immense strength and power, and a geasa that comes with a prophecy of how one will eventually die will allow them to evade said circumstances for many years to come.

One character of the Cycle of Kings who fell victim to the terms of his geasa was High King Conaire Mór, who is said to have been conceived when his mother met a beautiful bird which transformed into a man. Conaire becomes geasa-bound many years later, when he is visited by a flock of seabirds who revealed themselves to be his father’s band of warriors; they tell him that under no circumstances is he ever to hunt their kind. Other geasa they place on his upcoming kingship include that he must never follow thee red-clad warriors into a dwelling, and that he must never allow a woman into his abode after midnight. After a long and happy reign, Conaire’s end is a sad and gruesome one, as events transpire to force him to break each of his geasa in turn.

As a final note of interest, in 2014, evidence of the genetic imprint of a major player in the Cycle of the Kings, Niall of the Nine Hostages, was discovered by a team of Irish researchers; a find that we’re inclined to think ties this final, quasi-historical cycle of Irish myth into the present day with an rather poetic touch, indeed!


Do you have a favorite story from classic Irish mythology? Which cycle arrests your imagination the most? Tell us all in the comments below!