Grettis saga Ásmundarsonar ( listen (help·info)) (also known as Grettla, Grettir's Saga or The Saga of Grettir the Strong) is one of the Icelanders' sagas. It details the life of Grettir Ásmundarson, a bellicose Icelandic outlaw.
The saga is categorised as one of the Sagas of Icelanders (Íslendingasögur) all of which were written in the thirteenth and early fourteenth centuries and are fairly realistic accounts of events taking place between the ninth and the eleventh century in Iceland. The subject of such texts is usually conflicts over wealth, prestige, and power.
The author is unknown but it is believed that his story may have been based on a previous account of Grettir's life written by Sturla Þórðarson.
Grettir's intentions are not necessarily bad, but he is ill-tempered and often does things that he later regrets: he is also very unlucky, so some of his actions have severe, unintended consequences. Grettir spends most of his adult life in Iceland as an outlaw although he sails twice to Norway. He was related to King Olaf who Christianized Norway. But in Norway too he gets into trouble and is sent away. He is not involved in the viking raids that many other saga-heroes take part in.
Grettir is only introduced to the story in chapter 14. Up until then it tells of his father and grandfather who lived not uneventful lives. His grandfather Önundur from whom he may have inherited his physical strength had been a viking, and at one point fought a battle against Kjarval, who was king around Dublin. He settled at the northern coast of Iceland and had many sons. Grettir's life is told from beginning to end. As a child, he is rebellious and bad-tempered. He is described as red haired, somewhat freckled, and broad around the eyes. He is also courageous; he takes on and defeats the draugr Glámr, an undead being that is, in a sense, a corporeal ghost, strong and formidable. But the draugr curses him, and this is seen by the author as the cause of his later misfortunes.
Grettir is sometimes able to be a proper hero, defeating various enemies. But he is blamed for setting fire to a hall, killing many men, and is condemned to outlawry. This means that anyone can kill him without legal penalty and that people are forbidden to help him in any way; many infamous attempts are made on his life.
Grettir eventually becomes the longest-surviving outlaw in Icelandic history. When he had spent nearly 20 years as an outlaw, his friends and family ask for his banishment to be lifted, arguing that a man could not spend more than 20 years as an outlaw according to the law (in fact, there was no such law in medieval Iceland). After a debate at the assembly, it is decided that the outlawry will be lifted when he has completed the 20 years but not before. His enemies make one last effort, using sorcery to cause him to wound himself and finally defeat him, atop the cliff-sided, lonely, fortress-like Drangey off the northern tip of Iceland where he was staying with his brother Illugi, and his slave Glaumur.
Grettir Ásmundarson was reported to have been from Bjarg in Miðfjörður. At Bjarg, Grettir Ásmundarson always had refuge with his mother Ásdís. Many place names in the neighbourhood of Bjarg and indeed throughout the county bear the name of the outlaw e.g. Grettishaf, Grettistak and Grettishöfði at Arnarvatn. A memorial was erected to his mother Ásdís at Bjarg in 1974. The memorial displays a relief from Grettis Saga made by Icelandic artist Halldór Pétursson.
Grettir is celebrated in the long poem Eclogue from Iceland in the 1938 collection The Earth Compels by Irish poet Louis MacNeice, who had developed a love of Norse mythology while at school at Marlborough College. In it, the ghost of Grettir speaks with two men, Craven and Ryan, who have been 'hounded' from a decadent and war-threatened Europe 'whose voice calls in the sirens of destroyers'. He urges them to recover their underlying human values, and to assert, as he has, 'the sanctity of the individual will'. He tells them to return home as an act of duty, which he calls - remembering his own defiant choice to be an outlaw - 'Your hazard, your act of defiance and hymn of hate, hatred of hatred, assertion of human values' and (in the poem's final words') 'your only chance'.
- The Story of Grettir the Strong, Ch. 84, trans. by Eiríkr Magnússon and Willam Morris (1869).
- Bjarg in Miðfjörður (Historical Places in Northwest Iceland )
- Gettis Saga Ásmundarsonar, a critical, annotated scholarly edition by R. C. Boer (in German).
- Free downloads at ,  and 
- Full text and translations at the Icelandic Saga Database
- Proverbs in Grettis saga
-  Russell Poole, "Myth, Psychology, and Society in Grettis saga," Alvíssmál 11 (2004): 3–16.