Erc ingen Loarn sometimes Latinized as Erca to distinguish her from her grandfather Eirc mac Eochaid) was a queen consort of Ailech, best known as the eponymic mother of Muirchertach mac Ercae, a High King of Ireland.
Erca was born to an unknown mother and Loarn mac Eirc, a possible king of Dál Riata and a brother of Fergus Mór. She was married to Muiredach mac Eógain, a king of Ailech, to Irish Dál Riata.
In Ireland, Erca and Muiredach had four sons, including Muirchertach mac Ercae. After the death of mac Eógain, she married Fergus mac Conaill, another grandson of Niall Noígíallach. She gave birth to four sons in their marriage as well, including Feidhlimidh, the father of Saint Columba.
Dubhaltach Mac Fhirbhisigh details in his Leabhar na nGenealach Erca's death after a pilgrimage from Irish Dál Riata back to Britain. There she met her son-in-law, Saint Cairneach, who blessed her, told her half of Ireland's future kings would be her descendants, and promised her entry into heaven.
