Diarmuid Ua Duibhne

Diarmuid Ua Duibhne ( ) or Diarmid O'Dyna (also known as Diarmuid of the love spot) is a son of Donn and a warrior of the Fianna in the Fenian Cycle of Irish mythology. He is most famous as the lover of Gráinne, the intended wife of Fianna leader Fionn mac Cumhaill in The Pursuit of Diarmuid and Gráinne. Aonghus Óg or Aengus is Diarmuid's foster father and protector. Aengus owned a sword named Moralltach, the Great Fury, given to him by Manannán mac Lir. In The Pursuit of Diarmuid and Gráinne it is said of Moralltach that it left no stroke nor blow unfinished at the first trial. Aonghus gave this sword to his foster-son Diarmuid, in addition to a sword named Beagalltach, the Little Fury. Along with these two swords, Diarmuid is known to have wielded two spears, the smaller yellow spear Gáe Buide and the greater red spear Gáe Derg. These weapons were said to inflict wounds from which none could recover.

Diarmuid, while hunting one night, met a woman who was the personification of youth. After sleeping with him she put a magical love spot on his forehead; any woman that looked at the love spot fell instantly in love with him.

Gráinne, intended bride of Fionn mac Cumhail, fell in love with Diarmuid when she saw him in the wedding party. She laid a geis upon him to run off with her, with their long flight from Fionn aided by Aonghus Óg.

Eventually, Fionn pardons Diarmuid after Aonghus Og intercedes on their behalf; the pair settle in Kerry and produce five children. Years later, however, Fionn invited Diarmuid on a boar hunt, and Diarmuid was badly gored by a giant boar on the heath of Benn Gulbain. Water drunk from Fionn's hands had the power of healing, but when Fionn gathered water he would deliberately let it run through his fingers before he could bring it to Diarmuid. He had to be threatened by his son Oisín and grandson Oscar to play fair, but too late: Diarmuid had died. After Diarmuid's death, Aengus took his body back to the Brugh where he breathed life into it whenever he wanted to have a chat.

The story of Diarmuid and Gráinne is one of a number of instances in Irish mythology of the eternal triangle of young man, young girl and aging suitor. This theme is seen in the tale of Naoise, Deirdre, and Conchobar.

Diarmuid Ua Duibhne is said to be the founder of the Scottish Clan Campbell. On the Campbell crest is a boarshead, a nod to how Diarmuid died.