Oisín (pron.: // oh-SHEEN; Irish pronunciation: [ˈɔʃiːnʲ]), also spelt in English Ossian (pron.: // AW-shən) or Osheen, was regarded in legend as the greatest poet of Ireland, and is a warrior of the fianna in the Ossianic or Fenian Cycle of Irish mythology. He is the son of Fionn mac Cumhaill and of Sadhbh (daughter of Bodb Dearg), and is the narrator of much of the cycle.
His name literally means "young deer" or fawn, and the story is told that his mother, Sadbh, was turned into a deer by a druid, Fear Doirche (or Fer Doirich). When Fionn was hunting he caught her but did not kill her, and she returned to human form. Fionn gave up hunting and fighting to settle down with Sadbh, and she was soon pregnant, but Fer Doirich turned her back into a deer and she returned to the wild. Seven years later Fionn found his child, naked, on Benbulbin. Other stories have Oisín meet Fionn for the first time as an adult and contend over a roasting pig before they recognise each other.
In Oisín in Tir na nÓg, his most famous echtra or adventure tale, he is visited by a fairy woman called Níamh Chinn Óir (Niamh of the Golden Hair or Head, one of the daughters of Manannán Mac Lir, a god of the sea) who announces she loves him and takes him away to Tir na nÓg ("the land of the young", also referred to as Tir Tairngire, "the land of promise"). Their union produces Oisín's famous son, Oscar, and a daughter, Plor na mBan ("Flower of Women"). After what seems to him to be three years Oisín decides to return to Ireland, but 300 years have passed there. Niamh gives him her white horse, Embarr, and warns him not to dismount, because if his feet touch the ground, those 300 years will catch up with him and he will become old and withered. Oisín returns home and finds the hill of Almu, Fionn's home, abandoned and in disrepair. Later, while trying to help some men who were building a road in Gleann na Smól lift a stone out of the way onto a wagon, his girth breaks and he falls to the ground, becoming an old man just as Niamh had forewarned. The horse returns to Tir na nÓg. In some versions of the story, just before he dies Oisín is visited by Saint Patrick. Oisín tells the saint about what happened and dies.
In the tale Acallam na Senórach (Tales of the Elders), Oisín and his comrade Caílte mac Rónáin survived to the time of Saint Patrick and told the saint the stories of the fianna. This is the source of William Butler Yeats's poem The Wanderings of Oisin.
The location of the grave site of Oisín is disputed. It is rumoured to be in Glenalmond in Perth, Scotland. Wordsworth wrote a poem on the subject entitled "Glen-Almain, the Narrow Glen". Others say it is located in the Nine Glens of Antrim at a site that has been known for generations as "Oisín's Grave". The megalithic court cairn is located on a hillside in Lubitavish, near the Glenann River, outside the village of Cushendall on the North Antrim Coast, and is believed to be the ancient burial place of Oísín..
Macpherson's Ossian 
Ossian, the narrator and purported author of a series of poems published by James Macpherson in the 1760s, is based on Oisín. Macpherson claimed to have translated his poems from ancient sources in the Scottish Gaelic language. These poems had widespread influence on many writers including Goethe and the young Walter Scott, although their authenticity was widely disputed. Modern scholars have demonstrated that Macpherson based his poems on authentic Gaelic ballads, but had adapted them to contemporary sensibilities by altering the original characters and ideas and introduced a great deal of his own.
Other literary and film references 
- Oisín is a minor character in The Pursuit of Diarmuid and Gráinne from the Fenian cycle of stories.
- The poem "Ogum i llia lia uas lecht" in the Book of Leinster is ascribed to Oisín.
- Oisín, along with St. Patrick, is the main character of William Butler Yeats's epic poem The Wanderings of Oisin. He is also mentioned in Yeats's poem The Circus Animals' Desertion.
- Tír na nÓg is the name given to a large white horse in the Mike Newell film Into the West. In the story, Grandfather Reilly is followed to Dublin by this white horse, and gives it to his grandsons, Ossie (Oisín) and Tito. Grandfather tells them the horse is called "Tír na nÓg" and relates a version of the story of Oisín going to Tír na nÓg, the mythical Otherworld. As the family are travellers, Oisín is referred to in the grandfather's account as "the most handsome traveller who ever lived" rather than as the fenian character of legend. The horse is later confiscated by the police, but the boys steal it back, resulting in a chase across Ireland to the west coast.
- In The Fifth Generation, a novel written by Dale Jay Dennis, the lead male character relates the story of Oisín's travels to and return from Tir na nÓg as an allegory to human failings.
- In Shadowmagic, a novel and podiobook by John Lenahan, Oisín is the king of Tír na nÓg and the father of Connor, the lead character.
- The 1981 short animated film Faeries, is a loose adaption of the beginning of the Oisin and Niamh story.
- Oisin is a mentor of the main character that appears in the "David Sullivan series" of modern fantasy novels written by Tom Deitz.
Use in genetics 
- In Blood of the Isles, Bryan Sykes gives the populations associated with Y-DNA Haplogroup R1b the name "Oisín" for a clan patriarch, much as he did for mitochondrial haplogroups in his work The Seven Daughters of Eve.
- Beresford Ellis, Peter: "A Dictionary of Irish Mythology", page 189. Constable, London, 1987. ISBN 0-09-467540-6
- Gregory, Lady: "Gods and Fighting Men", page 149. Colin Smythe, 1987. ISBN 0-901072-37-0
- Heaney, Marie: "Over Nine Waves", page 214. Faber and Faber Ltd., London, 1994. ISBN 0-571-14231-1
- Murphy, Gerard: The Ossianic Lore and Romantic Tales of Medieval Irelan, page 24. Colm O Lochlainn (for the Cultural Relations Committee of Ireland), 1955.
- Beresford Ellis, Peter: "A Dictionary of Irish Mythology", page 159. Constable, London, 1987. ISBN 0-09-467540-6
- Thomson, Derick: The Gaelic Sources of Macpherson's "Ossian", 1952.
- An Chrannog: Lárionad Sealbhaithe & Buanaithe Gaeilge "http://www.crannog.ie/fff.htm". Accessed October 15, 2007
- Dennis, Dale Jay: The Fifth Generation. Horizon Publishers and Distributors, Bountiful, 1995. ISBN 0-88290-571-6 (Preview on Google Books)
- Oisín and Niam
- The Youth of Oisin
- Chisholm, Hugh, ed. (1911). "Ossian". Encyclopædia Britannica (11th ed.). Cambridge University Press.