Labraid Loingsech ("the exile, mariner"), also known as Labraid Lorc, son of Ailill Áine, son of Lóegaire Lorc, was, according to medieval Irish legend and historical tradition, a High King of Ireland. He was considered the ancestor of the Laigin, who gave their name to the province of Leinster. An early dynastic poem calls him "a god among the gods", suggesting he may once have been an ancestor-deity of the Laigin.
Labraid's grandfather, Lóegaire Lorc, had been High King, but was treacherously killed by his brother Cobthach Cóel Breg. Cobthach also paid someone to poison Lóegaire's son, Ailill Áine, who had taken the kingship of Leinster, and forced Ailill's young son to eat a portion of his father and grandfather's hearts, and to swallow a mouse. Struck dumb by the trauma, the boy became known as Móen Ollom, "the mute scholar". Later, he was hit on the shin during a game of hurling, and cried out "I am hurt!" From then on he was called Labraid, "he speaks".
The Lebor Gabála Érenn says Labraid was exiled overseas, and after thirty years made peace with Cobthach and was given the province of Leinster. Various versions of the story of Labraid's exile are told. In one, a prose tale in the Book of Leinster, Cobthach holds an assembly in Tara, and asks who the most generous man in Ireland is. His poet, Ferchertne, and harper, Craiftine, immediately answer "Labraid", so Cobthach exiles the three of them from his court. They take refuge with Scoriath, king of the Fir Morca in Munster. Scoriath has a daughter, Moriath, who falls in love with Labraid, but her mother always sleeps with one eye open to keep an eye on her. Craiftine plays a slumber-strain on his harp to put her completely to sleep, and Labraid spends the night with Moriath. When her mother wakes up she realises what has happened, Labraid confesses and the pair are married. With the help of Scoriath's army and Craiftine's harp, Labraid invades Leinster, and founds a kingdom there.
In other versions Labraid is exiled not to Munster but to continental Europe, to France or Armenia, where he gains great fame as the leader of the bodyguard of the king of that land, who is related to Labraid's grandmother, Cessair Chrothach. Moriath, hearing of his great deeds, falls in love with him from a distance. She writes a love song for him, and sends Craiftine to sing it to him. Labraid is delighted with the song, and decides to return to Ireland and reclaim his territory. The king equips him with ships and 2,200 men. His followers are known as Laigin after the broad blue-grey iron spearheads (láigne) they use. T. F. O'Rahilly attempted to explain the confusion over the location of Labraid's exile by suggesting that "Armenia" and the "Fir Morca", Moriath's people in Munster, are corruptions of Armorica in north-west France.
In some versions of the story Cobthach is killed in Labraid's invasion of Leinster, but in the Lebor Gabála and the Book of Leinster tale Labraid and Cobthach make peace. However, this peace breaks down. The Lebor Gabála says there was war between them. In the tale in the Book of Leinster, Labraid invites Cobthach, along with thirty kings of Ireland, to visit him, and builds an iron house at Dind Ríg to receive them, which takes a year to build. Cobthach refuses to enter the house unless Labraid's mother and jester go in first. They do so. Labraid serves his guests food and ale, and chains the house shut. With the aid of 150 pairs of bellows, he burns the house down, and Cobthach and 700 of his men, along with Labraid's mother and jester, are roasted to death. The jester had been promised that his family would be freed, and Labraid's mother was happy to die for the sake of her son's honour.
The story is told, similar to a legend of the Greek king Midas, that Labraid had horse's ears, something he was concerned to keep quiet. He had his hair cut once a year, and the barber, who was chosen by lot, was immediately put to death. A widow, hearing that her only son had been chosen to cut the king's hair, begged the king not to kill him, and he agreed, so long as the barber kept his secret. The burden of the secret was so heavy that the barber fell ill. A druid advised him to go to a crossroads and tell his secret to the first tree he came to, and he would be relieved of his burden and be well again. He told the secret to a large willow. Soon after this, however, Craiftine broke his harp, and made a new one out of the very willow the barber had told his secret to. Whenever he played it, the harp sang "Labraid Lorc has horse's ears". Labraid repented of all the barbers he had put to death and admitted his secret.
He ruled for ten, nineteen or thirty years, depending on the source consulted, and took vengeance on Cobthach's children, before being killed by Cobthach's son Meilge Molbthach. His children included a son, Ailill Bracan, whose son, Óengus Ollom, is included in the traditional list of High Kings. Other descendants considered High Kings include Fergus Fortamail, Crimthann Coscrach, Nuadu Necht, and Conchobar Abradruad.
Medieval Irish chronology is artificial and extremely inconsistent. The Lebor Gabála dates Cobthach's death and Labraid's accession to Christmas Eve, 307 BC, and also synchronises his reign to that of Ptolemy III Euergetes (246-222 BC). The chronology of Keating's Foras Feasa ar Éirinn dates his reign to 379-369 BC, the Annals of the Four Masters to 542-523 BC. Leinster genealogies are so long they imply a date in the 6th century BC at the latest. Francis J. Byrne suggests that these genealogies have been artificially lengthened by combining the genealogies of three originally separate peoples, the Laigin, Gáileóin and Domnainn, who made up the later Laigin. O'Rahilly considers Labraid the ancestor-deity of the Laigin, rather than a historical personage, but believes that his story reflects historical reality: Labraid's return from exile represents the original arrival in Ireland of invaders from Gaul who became the ancestors of the Laigin, an invasion he places in the 2nd century BC.