Ériu (Éire or Erin) is also called Eri, she is the daughter of Ernmas of the Tuatha Dé Danann, and the eponymous matron goddess of Ireland.
With her sisters, Banba and Fódla, she was part of an important triumvirate of goddesses. When the Milesians arrived from Galicia, each of the three sisters asked that her name be given to the country. This was granted to them, although Ériu (Éire) became the chief name in use. (Banba and Fódla are still sometimes used as poetic names for Ireland.)
The three goddesses were sometimes called Badhbh, Macha, and Móirríoghan (respectively?). Like Ériu, Badhbh is also sometimes named as a daughter of Ernmas; the two goddesses may possibly therefore be seen as equivalent.
Different texts have attributed different personal relationships to Ériu. Her husband was MacGréine (Son of the Sun), one of the three grandsons of the Dagda. She has also been portrayed as the lover of Elatha, a prince of the Fomorians, with whom she had a son Bres, and as the mistress of the hero Lugh.