Irish mythology 101: a fascinating overview

The Irish are known as world-famous storytellers—it’s in our blood. Here’s a taste of ancient Irish mythology and a glance at our folklore.

Myths are tall tales passed down from generation to generation. They play a fundamental role in any given society and generally rotate around narratives involving gods and goddesses, great heroes, and the forces of evil.

Mythology in Ireland predates history and stretches back centuries. Similar to many cultures, Irish folklore is impressive, fantastical, remarkable, and often bizarre.

Predating Christianity in Ireland – traced to 432 AD with the arrival of Saint Patrick – Irish mythology was documented and preserved only through word of mouth. Once Christianity was established, the tales were documented in early medieval manuscripts and would live long into the modern-day.

Deirdre is a legendary figure in Irish mythology. She was as beautiful as she was dangerous.
“Deirdre” by Helen Stratton

It is clear that much of ancient Irish folklore has been lost in translation, through the passing of time, and lack of documentation.

Saying that what we have recovered from our ancient past is enough to provide clarity on Irish mythology, in that there are four ‘cycles’: the Mythological Cycle, the Ulster Cycle, the Fenian Cycle, and the Historical Cycle.

Let’s take a look at an overview of Irish mythology, where it began, and how it came to shape a society based on the art of tall tales and storytelling.

Mythological Cycle

The Mythological Cycle was the first era of ancient Irish folklore and, as a result, is the least documented.

Stories from the Mythological Cycle centre on gods and the first settlers on the island of Ireland. Seven distinct groups frequent tales of the Mythological Cycle. These include:


Cessair (or sometimes Cesair) is a mythological figure in Irish folklore featured in the ancient medieval text, the Lebor Gabála Érenn. As per the narrative, she was the leader of the first settlers in Ireland.


The Fomorians were a supernatural race in the Mythological Cycle of Irish mythology.
“The Fomors (or The Power of Evil Abroad in the World)” by John Duncan

This supernatural race, according to Irish mythology, was a dark and hostile group who resided underground and sometimes underwater. In texts, they are depicted as large, monstrous creatures.


The Partholinians were the second group of settlers on the Emerald Isle. They are said to have introduced traditional activities such as farming, cooking, and building.


This group are told to be the third that settled in Ireland. They arrived some thirty years after the Partholinians died out, but became extinct before long, according to the Mythological Cycle.


The Firbolg ambassador meets with the Tuatha Dé Danann's ambassadors. Both were key races in Irish mythology.
Illustration by Stephen Reid. The Firbolg ambassador meeting the Tuatha Dé Danann ambassador.

As per storytelling from the Mythological Cycle, this group of people were the fourth to settle on the island of Ireland. It is said that the Firbolgs were descendants of the Muintir Nemid, a race which previously inhabited the island before moving on to Europe.


The Milesians are considered the last group to settle on the island of Ireland. They represent the Irish people. It is said that on arrival they contended with the Tuatha Dé Danann who were, at that time, the representation of Pagan Ireland.

Tuatha Dé Danann

The Riders of Sidhe, a group of the Tuatha Dé Danann that were known as great gods in Irish mythology.
“The Riders of the Sidhe” by John Duncan

The Tuatha Dé Danann are the most remembered supernatural race of Irish folklore in the Mythological Cycle. They are said to represent pagan gods in pre-Christian Ireland.

Ulster Cycle

This was the second “cycle” of Irish mythology. Most of its tales originate from the 1st-century AD. For the Ulster Cycle, many of its myths take place in the provinces of Ulster and Connacht and centre around births and death, training and battle in the Irish countryside.

There are many tales from this cycle, featuring kings and heroes, gods, friends and foes. Some of the most important include:

 Táin Bó Cúailnge

This early medieval epic tells the tale of a war between Ulster and Connaught, led by Queen Medb and her husband Ailill.

The Tragic Death of Aife’s only Son

Cú Chulainn riding into battle. He was an iconic, tragic hero in Irish mythology.
Cú Chulainn racing into battle.

This is another major player in the Ulster Cycle. This tale from ancient mythology tells of the hero Cú Chulainn, who, while training overseas, leaves his pregnant wife on the island of Ireland. It is a story of family and love, battle and loss.

Bricriu’s Feast

This story from the Ulster Cycle actually dates back to the 8th-century AD and tells of warriors in battle. It is mentioned numerous times in ancient mythological manuscripts.

The Destruction of Da Derga’s Hostel

This mythological tale tells of birth and loss, death and destruction. The narrative features  Conaire Mór, a legendary High King of Ireland.

Fenian Cycle

Fionn mac Cumhaill battling Aillen, a fire breathing Tuatha Dé Danann member. Fionn was a valiant warrior in Irish mythology.
Illustration by Beatrice Elvery; Fionn fighting Aillen.

The Fenian Cycle is the third wave of Irish mythological texts. Like its predecessor, it is focused on heroes and heroines and the stories are generally based in the regions of Leinster and Munster.

Stories from this cycle centre on the Fianna – a band of independent warriors – and their leader, Fionn mac Cumhaill. Key texts from this cycle include:

 Acallam na Senórach

This famous text from the Fenian Cycle tracks conversations between the final remaining members of the Fianna and Saint Patrick.

Tóraigheacht Dhiarmada agus Ghráinne

This is another ancient tale from Irish mythology of the Fenian Cycle. According to folklore, this story tells of a love triangle between Fionn mac Cumhaill, princess Gráinne, and her lover Diarmuid Ua Duibhne.

Tír na nÓg

Niamh and Oisín travelling to Tír na nÓg, the mythical land of everlasting life in Irish mythology.
Illustration by Stephen Reid. Oisín and Niamh travelling to Tír na nÓg

In Irish mythology, Tír na nÓg is the supernatural fantasy realm of everlasting youth and beauty. In the eponymous tale, two lovers travel to this world on a magical horse that can transcend water.

Historical Cycle

St. Patrick was a member of the Historical Cycle of Irish mythology.

This is the last cycle of mythology. Stories from this time were blended factual history with legends and tall tales, the reason behind its name, the “Historical Cycle”.

Folklore from this cycle includes very real figures in Irish history, as well as purely mythological creatures. Only one main tale from this cycle need be noted:

Buile Shuibhne

Written in the 12th century, written in both verse and prose, it tells the story of curses and supernatural powers. 

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