There are several myths and legends associated with Benbulben, and one of the most famous of these being The Boar of Benbulben. Legend has it that King Cormac, the High King of Ireland, had betrothed this daughter Grainne to the warrior Fionn Mac Cumhaill (Finn McCool). However, rather than marry the aging McCool, the rebellious Grainne elopes with the young Fianna warrior Diarmuid Ua Duibhne.
The enraged Fionn pursues the couple the length and breadth of Ireland and catches up with Diarmuid on the slopes of Benbulben where he tricks him into fighting an enchanted wild boar. After a fierce and drawn out battle Diarmuid manages to slay the boar with his sword but not before the beast was able to pierce his heart with its tusk. The dying Diarmuid asks Fionn to bring him water from a nearby holy well which he says will save his live. Fionn brings him the water but then opens his hands to let it trickle out between his fingers.
One version of the story has it that Fionn cut Diarmuid’s head off and when he showed it to Grainne she died on the spot from grief. The couple are said to be buried in a cave that now bares their name on the Dartry mountain range, not far from the slopes of Benbulben.