The next group to arrive in Ireland was the Firbolgs. The Firbolgs were actually descendants of the Nemedians, who fled Ireland from both the war against the Fomorians and the plague that ravaged their population. Semion, great-great-grandson of Nemed had brought his followers to Greece, but they suffered from slavery and oppression at the hands of their Greek masters.

It was the five sons of Dela, descendants of Semion, who took his people out of slavery in Greece and Thrace, bringing them back to Ireland, 230 years later.

The sons of Dela (Firbolgs) divided Ireland between themselves, but their power in Ireland only lasted for 37 years before the Tuatha Dé Danann arrived. The Firbolgs were often seen as inferior people, and strangely, quite primitive to the Tuatha Dé Danann, and later the Milesians.

Tailtiu was the daughter of King of the Mag Mor ("Great Plain"), from the Land of the Dead, which was a poetic name for Spain. Tailtiu married to the last Firbolg king, Eochaid Mac Eirc, who died in the First Battle of Moytura. At her husband's death, she married again Eochaid Garb Mac Dúach, a Danann warrior. Since she was the foster-mother of Lugh, she was held in honour at the Lugnasad by the Tuatha dé Danann.

Not much was known about these people, except with their dealing with other settlers. They did not seem to have any trouble with the Fomorians. The Firbolgs, however did not like the Tuatha Dé Danann, and fought the First Battle of Moytura, before they were defeated. The Firbolgs lost the battle because the Dananns had technological superior weapons.



The Firbolg warrior Fer Díad, was the companion of Cú Chulainn. He was one of Medb's champions who fought against Cú Chulainn in single combat. Fer Díad was killed after three-day fighting.