Diarmaid & Grainne

This story is often told as "The pursuit of Dairmaid and Gráinne"

Fionn Mac Cumhaill now an ageing man and a widower hears that Cormac mac Airt  the high king at Tara (His reign as high king in Ireland is said to have been from 227 to 266 A.D) has a beautiful daughter called Gráinne and sends a messenger to Tara conveying his intentions to marry her. With Cormac's blessing and Gráinne's agreement the wedding banquet is set.
At the feast at Tara on the wedding day all the warriors of the Fianna were there and Gráinne could'nt help noticing the most handsome of them all, Diarmaid.
Gráinne called her head maid and secretly told her to concoct a sleeping potion enough for everyone at the feast. When the potion was ready it was slipped into the drinks of everybody there  except for Diarmaid's, and when everyone was soundly asleep Gráinne approached Diarmaid and asked him to run away with her, he refused but Gráinne placed a Geis on him to follow her and Diarmaid being a warrior of the Fianna had to obey any Geis put on him. They left Tara and crossed westwards across the river Shannon in search of Aonghus, Diarmaid's foster father. Aonghus was a magical figure who had links with the Tuatha De Dannan.
The next day when Fionn awoke from his deep sleep he quickly became aware of Gráinne and Diarmaid's absence and what had been done. He set about planning revenge and soon afterwards started out in pursuit with the rest of the Fianna.
The Pursuit is said to have taken 16 years spanning the length and breath of Ireland, it is also said that Diarmaid & Grainne slept on many occasions on the many Dolmens scattered around the countryside and so these ancient Dolmens (pictured below) are sometimes referred to as "The beds of Diarmaid and Gráinne". On many times Fionn came close to catching up with Diarmaid and Gráinne but they make their escape each time with the aid of Aonghus. Their travels brought them in contact with a young warrior named Muadháin, who became their servant and helped to fight off mercenaries along the way.

At first Diarmaid did not love Gráinne but it was when they came to a forest in the south west of the country that he fell in love with her. In The forest was a magical tree bearing magical fruit but the tree was guarded by a giant of a man with one eye called Searbhán. He lived high up in the branches of the tree, and was so fierce that no one dared challenge him not even the mightiest warrior of the Fianna. Diarmaid befriended Searbhán and the fugitives were invited to live in the tree but were warned not to touch the fruit scattered about its branches. Gráinne became pregnant afterwards and craved some of the beautiful fruit but Searbhán refused Diarmaid to fetch some fruit so a mighty battle started between the two which followed by Diarmaid killing the giant. 

While living in the north of Connacht Diarmaid heard of a hunt involving Fionn and the Fianna. They were all hunting a great Boar that lived around Ben Bulben in north Sligo. Diarmaid heard that many of the Fianna had been killed trying to bring down the Boar so he decided to join the hunt ignoring Gráinne's pleading not to go, he was also aware of a prophesy he heard as a young boy which stated that he would meet his death by a great Boar!
On top of the mountain Diarmaid caught sight of the animal and swiftly pursued it until he was within striking distance but the Boar turned and charged him, Diarmaid side stepped and leaped on the Boar's back and after much struggling the Boar tossed Diarmaid from its back ripping his stomach but with the last fading piece of energy Diarmaid pushed his sword into the Boar killing it. Soon after Fionn and the rest of the Fianna caught up to the dying Diarmaid, Oisín asked Fionn to fetch some water for his dying friend but he was met with a refusal, Oisín asked again but when Fionn returned with water Diarmaid had passed away. Diarmaid's foster father Aonghus came and took him to his magical palace on the banks of the river Boyne and Fionn finally married Gráinne.