Fóstbrœðra saga (listen^ⓘ) or The Saga of the Sworn Brothers is one of the sagas of Icelanders. It relates the deeds of the sworn brothers Þorgeir and Þormóðr in early 11th century Iceland and abroad. Þorgeir is a capable and insanely brave warrior. He kills people for trifles and for sport. Þormóðr is a more complicated character; warrior, trouble-maker, womanizer and poet. The saga contains poetry attributed to him, including parts of a lay on his blood brother. It is said that a cairn called Þorgeirsdys, identifies the place of death and burial of Þorgeir. This is located on the Hraunhafnartangi peninsula, just south of the modern lighthouse.^[1]

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The saga survives in three early manuscripts. Each has a rather different version of the text:

• Hauksbók (earlier fourteenth century), beginning missing due to lost pages
• Möðruvallabók (mid-fourteenth century), end missing due to lost pages
• Flateyjarbók (c. 1390)

The date of composition of the lost written archetype of Fóstbrœðra saga has been the subject of considerable dispute. Sigurður Nordal argued for ca. 1200 (Björn K. Þórólfsson and Guðni Jónsson 1943: lxxii) whereas Jónas Kristjánsson argued for the end of the century (1972, 310). There is no clear consensus, though Andersson's 2013 analysis preferred an early dating of 'presumably not much later than 1200' (2013, 72).

A long-standing controversy centers on which manuscripts represent the most original version. In particular, the debate has focused on several unusual "clauses" (Icelandic klausur) or asides in the saga which do not fit in with conventional saga style. These have been understood both as late interpolations and as signs of an early, developing saga style (Jónas Kristjánsson 1972).

The skaldic stanzas attributed to Þormóðr kolbrúnarskáld Bersason appear genuine (according to Guðni Jónsson in Björn K. Þórólfsson and Guðni Jónsson 1943: lxi); he would have composed ca. 1010-1030 (according to Guðni Jónsson in Björn K. Þórólfsson and Guðni Jónsson 1943: lxix).

In the words of Lee M. Hollander (1949, 75),

The saga of the Sworn Brothers, Thorgeir and Thormod, occupies a position of secondary importance among the Old Icelandic family sagas—at least, it is not a favorite. There are good reasons for this: it does not have the scope and weight of such sagas as Njála, Eigla, Laxdæla, nor the depth and classic form of such as Hrafnkels saga, Gísla saga, Thorsteins saga hvíta; nor do students of Germanic antiquities value it because of any wealth of specific information on the history, religion, culture, laws of the Old North.

However, the saga has recently come to critical attention for the range and detail of its portrayals of women (Gos 2009).

The saga is the basis for Halldór Laxness's novel Gerpla,^[2] and a key source for Dauðans óvissi tími, a 2004 novel by Þráinn Bertelsson.^[3]

For a full bibliography of Fóstbræðra saga see Ryan E. Johnson, 'From the Westfjords to World Literature: A Bibliography on Fostbræðra saga', Scandinavian-Canadian Studies/Études scandinaves au Canada, 26 (2019), 312–19.