The Firbolg queen and the foster mother of Lugh.

Tailtiu was a daughter of Mag Mor the Slow, who the King of Spain. Tailtiu had first married Eochaid Mac Eirc, the king of the Firbolgs. At her husband's death, she remarried Eochu Garb, son of Dui Dall, who was a Danann. It was during her marriage to Eochu Garb that she became foster mother to Lugh, son of Cian, who was a son of the Danann physican Dian Cecht, and of Ethniu, who was daughter of the Fomorian king, Balor.

Tailtiu died in the town, which Lugh named in her honour. Lugh also created a festival, Lughnasadh, in her honour.