("fair mane") was the wife of the legendary Irish High King Eochaid Mugmedon
and mother of his eldest three sons, Brion
. She was the sister of Crimthann mac Fidaig
, king of Munster
, whom she is said to have poisoned.
She was the first wife of Eochaid; he took a second wife, who gave birth to Niall of the Nine Hostages. Several stories depict Mongfind as an adversary of her stepson.
According to Cormac's Glossary, she was a goddess the pagan Irish worshipped on Samhain. Later legend, as documented in PW Joyce's Social History of Ancient Ireland, makes Mongfind a bean sidhe.