Queen Medb of Connacht
Queen Medb is the cause of the invasion of Ulster, albeit unwittingly. She does not like having less wealth than her husband and vows to redress this by acquiring a stud bull like his. When she cannot do this peacefully she invades Upster to get her way with force. She is a strong and warrior-like and commands respect among the armies under her. She is fearless.
King Ailill of Connacht
Although not a particularly important character in his own right, Ailill is nonetheless pivotal as it is his wealth that engenders envy and the desire for marital equality in his wife and ultimately causes the invasion of Ulster.
Finnbhennach the Bull
King Ailill's stud bull was born into the herd that belonged to the Queen but his nose was rather out out of joint by this and he does not like being in a herd that belongs to a woman. He therefore leaves her herd and joins the herd belonging to the King. This generated the Queen's obsession with getting an alternative stud bull.
Donn Cuailnge the Bull
The stud bull is loaned to the Queen until it is learned that she would have taken him anyway. This starts the war between the houses of Connacht and Ulster. Although the Queen manages to take possession of him he ends up killing Finnbhennach and himself dies from exhaustion after traipsing around Ireland terribly wounded.
Cu Chulainn
Cu Chulainn is the hero of the text. He is a seventeen year old upon whose shoulders falls the ask of single-handedly defending Ulster from the invasion. He is a courageous and strategic fighter. He manages to get an agreement from the invaders that the battle will be in the form if hand-to-hand combat at which he is highly skilled and seemingly tireless. He is also the chief link in the story between the human and mythical worlds. He proves himself to be an honorable man who keeps his word.
Morrigan
The Morrigan is a mythical character who has the ability to change form and take on both human shape and that if other creatures. She becomes an eel and a heifer and in both guises she is a danger to Cu Chuliann.
Lugh
Another mythical figure, Lugh is Cu Chuliann's father. He puts his son to sleep for three days so that he can tend to his terrible wounds.
Fergus
Fergus is Cu Chulainn's foster father and is fighting on the Connacht army. He had been king in Ulster, but his consort Ness convinces Fergus to let her son, Conchobar, rule for a year. Conchobar is so well-liked that Fergus loses the crown and is later sent into exile and flees to Connacht, joining forces with Ailill and Medb. Fergus and Cu Chulainn engage in combat but are saved from this altercation when Cu Chulainn offers to yield to him if he does the same when they next meet. Fergus is a man of honor and he abides by this arrangement.
Ferdia/ Fer Diad
He was Cu Chulainn's foster-brother, who had trained with him under the warrior woman Scathach. Cu Chulainn had surpassed Ferdia at the use of the Gae Bulg, a barbed spear. Medb promises Ferdia her daughter's hand in marriage if he will fight his foster-brother. Ferdia agrees and the single-combat lasts for a long time before Cu Chulainn uses the Gae Bulg on Ferdia, killing him.
Findabair
She was Ailill's and Medb's daughter, who offer her hand in marriage to any warrior willing to fight Cu Chulainn. Her husband, Fraech, had refused to pay the large sum that Ailill and Medb requested as Findabair's bride-price and instead fights Cu Chulainn in single-combat and is killed. Medb then uses her daughter as bait for countless warriors to fight Cu Chulainn, even Ferdia is encouraged by the prospect of marriage with Findabair to fight his own foster-brother. The 7 Kings of Munster, who had been promised Findabair find that she had spent the night with another warrior and wage a battle with Ailill, resulting in the death of 700 men. Findabair dies of shame after hearing how she had inadvertently caused the death of so many men.
Laeg
Laeg is Cu Chulainn's charioteer and companion. He helps Cu Chulainn prepare for battle and acts as moral support during Cu Chulainn's combat.
