Captain of the Fianna (rígfhéinnid) and chieftain of Clan Baiscne. Cumhaill (Cumhall or Cool) was the son of Trenmor and descendant of Baíscne. Cumhaill was also the brother of Crimmal.

Cumhaill married Muirenn, daughter of Tadg and granddaughter of Nuada of the Silver Hand. Cumhaill was the father of Finn.

Before his son was born, Goll Mac Morna had challenged Cumhaill for the leadership of the Fianna. Cumhaill's father-in-law had opposed his daughter marriage to Cumhaill. Tadg conspired with Goll to overthrow and kill Cumhaill.

A clan war was fought at Cnucha (Knock), not far from Tara. Tadg used his magic to confuse and strike fear upon Clan Baiscne. Cumhaill began to suffer from sudden weakness due to Tadg's magic. Yet, Cumhaill managed to wound Goll, taking out one of his eyes, but Cumhaill was killed by Lia, lord of Luachar.

Crimmal was the son of Trenmor, and brother of Cumhaill. Crimmal was one of the survivors when Clan Morna defeated Clan Baiscne in the battle of Cnucha (Knock).

When Finn decided to become leader of Clan Baiscne, Crimmal and his small group of survivors joined his nephew.

The greatest Fianna warrior in the Fenian cycle. Finn was the son of Cumhaill and Muirenn (Muirne, Murna), daughter of the druid Tadg and the granddaughter of Nuada of the Silver Hand.

During the reign of Conn, his father died before he was born, in a clan war against the Clan Morna; when Goll Mac Morna challenged Cumhaill leadership of the Fianna (rígfhéinnid). Muirenn fled with two nurses to a forest Slieve Bloom, where he was born. One of these nurses was Muirenn's sister, named Bodhmall. Muirenn called him Demna, but one of his nurses called him Finn, which means "the Fair One". To prevent the men of Morna from killing his son, Muirenn left Finn in the care of the two nurses, hoping to draw the Morna away from the forest. One nurse was named Liath Luachra or Liathluchra, while the other was the druidess Bodhmall, possibly the sister of Muirenn.

As Finn became a young man, he set about becoming chieftain of Clan Baiscne and restoring his clan to the Fianna. Finn had to undergo a series of tests, set up by the Fianna. After successfully completing all the requirements, the Clan Baiscne rejoined the Fianna and Finn became the chieftain of his clan. Cormac Mac Airt only awarded Finn with the leadership of Fianna, when he saved Tara and killed a goblin.

Finn has a pair of hunting hounds, named Bran and Sceolang. The mother of Bran and Sceolang, was actually a Danann woman, named Uirne or Tuirn, who was transformed into a she-dog while she was still pregnant, by a jealous mistress of her husband. Uirne regained her human form, after she gave birth to Bran and Sceolang, but her sons remained in the form of the hounds. Uirne was the sister of Muirenn and aunt of Finn. So these hounds were actually Finn's cousins. The hounds were known for its speed and their human intelligence. In other tales, Finn has a third hound, Lomair (possibly sibling of Bran and Sceolang) or Adnúall.

Finn married the hind-woman named Sadb (Saba or Blái), whom a Dark Druid had fallen in love with. However, the Dark Druid abducted Sadb during his absence in a war. Though, Finn never saw Sadb again, the hero did find their son, whom he named Oisín (Oisin).

Finn had other children by other women. In the Acallam na Senórach, he was the father of Raige Rosclethan (the "Wide-Eyed") and Caince Corcairderg (the "Purple-Red"). Finn was also the father of a son named Dáire Derg, and of a daughter named Lugach. Dáire slept with his sister when he was drunk at Taurmore. Lugach begotten a son named Mac Lugach. Finn blessed his grandson, naming him Gaine ("Blessing"). At the time, Lugh was married to Mongfinn.

Finn also had a son named Fiachna and a foster-son, named Innsa, the son of Swena Selga, who appeared in the Hostel of the Quicken-Tree.

Finn became less of an ideal and romantic hero, as he grew older. Finn was past his prime when he was engaged to Gráinne (Grainne), daughter of Cormac Mac Airt. However, Grainne was in love with the younger companion of Finn, Díarmait, whom she eloped with. Finn pursued the young couple, until Cormac forced Finn make peace with them. When Díarmait was mortally wounded by a boar, Finn, who never forgiven his former comrade, let the healing water, slipped from his fingers. Díarmait died from his wounds.

There are several accounts of his deaths. There was even story, which Finn did not die, that he slept in the Otherworld until Ireland face great danger.

According to Cath Gabhra (The Battle of Gabhair), five men had murdered Finn at Garristown. While in the Aided Finn (The Violent Death of Finn), Aichlech Mac Dubdrenn killed Finn in battle at Ath Brea (Ford of Brea).

A warrior-bard. Oisín (Oisin) was the son of Finn Mac Cumhaill and Sadb (Saba or Blaí), the woman-hind. See Sadb and the Birth of Oisín in the Fenian Cycle.

One tale tells of how he and Caílte Mac Ronan survived the Battle of Gabhra, in the Acallam na Senórach ("Colloquy of the Ancients"). Oisín parted company with Caílte, but later meeting his companion in Tara, where he encountered St Patrick. Caílte and Oisín reminisced a number of adventures of the Fian warrior, particular of Finn.

In another tale, Oisín survived the Battle of Gabhra and met St Patrick, 300 years later. A beautiful Danann woman, named Niam of the Golden Hair, had lured Oisín to the Otherworld. They became lovers.

Later, when he decided to return to the surface, Niam warned him to not set foot to the surface, but to remain mounted on a magical horse. He broke this geis, and was transformed into an old man. Oisin discovered that all his companions were dead for three hundred years.

Oisín then met St Patrick, where he told saint of his life with his father (Finn) and the adventures of the Fianna. Several adventures are recounted in the Otherworld. Patrick had Oisin's tales recorded. Before the hero died, he was baptised.

It was Oisín who found the horn borabu under the rock. The borabu was sounded to summon Fian warriors from all parts of Ireland.

Oscar was the son of Oisín (Oisin) and Eibhir, and the grandson of Finn.

Oscar was the strongest and fiercest fighter of the Fianna. Oscar appeared frequently in battles. In his first battle, he was in love with Níam, the daughter of Áed Donn, who was king of Ulster. But Níam was betrothed to Áed, the son of King Fidach of Connacht. Áed received aids from Ulster and Leinster in the war against the Fianna. In the fighting, Oscar beheaded Áed, and also killed Áed Donn and Baetán, the king of Leinster. Oscar won Níam.

In Bruidhean Chaorthainn (Fairy Palace of the Quicken Trees), Oscar swept off the head of Sinsar, the King of the World, in the battle on the ford of Shannon.

In the Fianna was defeated in the Battle of Gabhra. Oscar killed Cairbre, high king of Ireland in single combat, but he was also mortally wounded in this encounter.

Mac Lughach was another better known grandson of Finn Mac Cumhaill. But according to one early text, Mac Lughach was the son of Lugaid Lága.

However, in some later texts, such as Acallam na Senórach, Mac Lughach had different parents. Finn had a son named Dáire Derg and a daughter named Lugach. One day in Tara, while Dáire Derg was drunk drinking from ales, Dáire slept with his sister. So from this incestuous union, Mac Lughach was born.

Whoever were Mac Lughach's parents, Finn had placed his grandson in the care of Mongfhind (Mongfinn), the nurse and teacher of the Fianna, until he was twelve. But in Acallam na Senórach, Mongfhind was Finn's wife. Then Mongfhind gave the boy a full set of armour and weapon, and sending Mac Lughach to his grandfather in Sliab Bladma (Slieve Bloom), for military training with the Fianna.

At thirteen, Mac Lughach caused distress among some Fian men, because the boy could out-hunt them. The entire Fianna complained to Finn that Mac Lughach must leave. When Finn discovered that they were jealous of the boy agility and skills with the weapon in the hunt, his grandfather gave Mac Lughach a number of advice how to behaviour.

Mac Lughach was one of Finn's trusted warriors, skilled with the weapon and music. He fought in the Battle of Gabhra, where Bresal, son of Éirge and grandson of King of the Irish Vikings killed Mac Lughach.

A Fian bard-warrior. Caílte (Cailte) was sometimes called the nephew of Finn Mac Cumhaill. Caílte was the son of Ronan (Ronain), and he was probably a chieftain of his own clan as Clan Ronan. There are several variation of spelling to Caílte's name, including Caoilte, Caolte, Keelta and Kylta.

Caílte was known for his bardic skills in poetry and his fleetness of foot.

Caílte was best known in the Acallam na Senórach (The Colloquy of the Ancients), where the aged hero met St Patrick. Caílte and Oisin, the son of Finn Mac Cumhaill, were the only surviving Fian leaders who fought the Battle of Gabhra.

Caílte travelled throughout Ireland with St Patrick, recounting the various brave deeds of Finn and their other comrades.

Díarmait ua Duibne or Diarmaid O'Dyna was the son of Donn and the foster son of Angus Óg. Díarmait was one of the warrior and companion of Finn Mac Cumhaill. In the Acallam na Senórach, Caílte had called Díarmait, his foster-brother.

Before he was born, his father had killed the son of his wife and her lover, Roc, steward of Angus Óg. Roc ressurected his son, but the boy was transformed into a wild boar. Roc ordered the boar to find and kill Díarmait.

As a Fian warrior, Angus Og and Manannán Mac Lir gave Diarmait some formidable weapons. Diarmait used the Gáe Dearg or Gáe Derg, "red spear", and his sword Nóralltach, "Great Fury", for adventure which are the matter of life and death. Diarmait also has the smaller "yellow spear", called Gáe Buide, and a sword named Begallta ("Little Fury") for lesser adventure.

Díarmait was often called Díarmait Ó Duibhne ("Díarmait of the Love Spot"), because one of the beautiful maiden (Danann?) placed a mark on his forehead, making the young hero irresistible to women. This mark would proved to be his undoing.

When Gráinne (Grainne), daughter of the Cormac Mac Airt, high king of Ireland, was betrothed to Finn. Grainne preferred young Díarmait to the older Fianna captain. Grainne tried to seduce Díarmait, but he refused her advances until she placed a geis upon the hero. Díarmait was left without a choice and eloped with her.

Finn learning of the news, he tried to hunt them down. A couple of Diarmait's adventures including the killing the three venomous hounds of the three sea-champions, and slaying the Searbhan (Sharvan), the guardian of the magic rowan tree (quicken tree). For sixteen years they managed to evade Finn's men, before Angus and Cormac persuaded Finn to make peace with the young couple. It was uneasy peace and Finn resented Díarmait for taking away his young bride and had never forgiven the younger man. By then, Díarmait was the father of four sons and a daughter.

Díarmait one day heard that the Fianna were hunting for a magic boar that roamed through the forest near Tara. Grainne was unable to convince her husband not to join Finn, knowing that doing so would mean his death.

The boar came upon Díarmait, resistant to the hero's weapons. Díarmait was mortally wounded. Finn, who had possessed healing water, allowed the water to slip through his fingers. Díarmait died from his wounds. His body was taken away by his Angus Og, his foster father, who preserved his body from decay and would occasionally given enough life to talk to Angus.

Grainne swore to avenge her husband's death. She told Finn that when her sons grew to manhood, they would seek the hero and kill him. However, Finn persuaded her to marry him. Grainne felt shamed when the Fian warriors mocked her. In the end, Grainne decided to make peace with Finn.

Díarmait was the hero of several other tales, including freeing Finn and other Fianna, who had been trapped in a fairy hostel, by killing the Three Kings of the Island of Torrent. See Bruidhean Chaorthainn (Hostel of the Quicken Trees)

A Fenian warrior with the gift of clairvoyance. Diorruing was the son of Dobar Ua Baíscne. Diorruing was the friend of Finn Mac Cumhaill.

Diorruing's skill with the second sight that enabled him to see the present and the future. In the Pursuit of Diarmait and Gráinne, it was he who advised the aging Finn that the most suitable wife to him would be Gráinne, the daughter of Cormac mac Airt, who was the high king of Ireland.

Diorruing was soon to regret this advice, because Gráinne preferred the younger hero, Diarmait, who was also his friend. When most of the people in her father's court, including her father and Finn, fallen into slumber, Gráinne placed a geis upon Diarmait to elope with her. Diarmait was troubled by his misfortune, because he was a great friend of his leader (Finn). Diarmait asked each of his companion, who were not in a drugged stupor, each one advised that he must do as Gráinne say, because of the geis she had place on the reluctant hero, including Cailte Mac Ronan, and Finn's own son and grandson, Oisin and Oscar.

Diorruing, the last companion to advise Diarmait, foretold his friend's death, but he also counselled Diarmait that he must do as Gráinne told, since the hero was under the geis.

Captain of the Fianna (rígfhéinnid) and chieftain of the Clan Morna. Goll was the brother of Conan (Mac Morna). Goll's real name was Aed, which means "Red".

Goll challenged Cumhaill for the leadership of the Fianna. Goll became captain of the Fianna after the death of Cumhaill and defeat of Clan Baiscne at the battle of Cnucha (Knock). Goll lost one of his eyes to Cumhaill in the battle. It was this reason that he changed his name from Aed to Goll, which means "One-eyed".

Years later, Goll lost the captaincy to Cumhaill's son, when Finn became a young man.

Later, the Fianna splited again during the reign of Cairbre. Goll and the Clan Morna sided with the high king. He led the Clan Morna against Clan Baiscne in the Battle of Gabhra.

Conan the Bald. Conan was the brother of Goll, clan leader of the Morna.

He was described as fat and ugly, Conan was never good warrior, performing no heroic achievements. He was renown for his cowardice and constant complaints.

In one amusing story, the Fian warriors came upon a hostel, where they were given food and hospitality. However, they discovered it was a magical trap set by the Fairy Folk. They were rescued by Díarmait. However, Conan became stuck to his seat. When they pulled him off his seat, some of his skins were tore from his buttocks and back. To compensate for the loss of skin, the Fian warriors covered him with the hide of a black sheep. This sheep hide grew in place of his skin.

Another funny tale, tell of a battle that took place in the "Hills of Slaughter". One enemy warrior challenged the bravest Fian to single combat. The Fian warriors pushed Conan to face the enemy warrior named Liagan. Liagan insulted and berated Conan. Conan, however, distracted Liagan, and when the warrior turned his head around, Conan swept the enemy's head off with his sword. The coward he was, Conan dropped his sword and ran back to his own line. The Fianna roared in laughter.

Lia was the Lord of Luachar, Connacht. Lia was the Treasurer of Clan Morna. During the ascendancy of Clan Morna, when Goll Mac Morna became captain of the Fianna, Lia became Treasurer of the Fianna. Lia took the treasure bag after killing Cumhaill, the captain of the Fianna. His station as Treasurer was that he guarded the magic treasure bag, made of skin of the crane. The bag was magical because it can hold many items not physically possible.

Finn avenged his father by killing Lia, taking back the treasure bag.

Lia was the father of Conan Mac Lia.

Conan (Mac Lia) was the son of Lia (treasurer of Clan Morna).

On a number of occasions, Conan Mac Lia tried to avenge his father's death, but he was never successful in killing Finn Mac Cumhaill. When finally trapped by his father's killer, Conan offered his services and swore allegiance to Finn. Finn graciously accepted Conan's vows, and the two enemies became steadfast friends.