thumb|Manuscript AM 122 a fol. Sturlunga saga (University of Iceland).
Sturlunga saga (often called simply Sturlunga) is a collection of Icelandic sagas by various authors from the 12th and 13th centuries; it was assembled in about 1300, in Old Norse. It mostly deals with the story of the Sturlungs, a powerful family clan during the eponymous Age of the Sturlungs period of the Icelandic Commonwealth.
Sturlunga saga mostly covers the history of Iceland between 1117 and 1264. It begins with ', the legend of Geirmundr heljarskinn, a regional ruler in late 9th-century Norway, who moves to Iceland to escape the growing power of King Harald Finehair. The more historical sagas commence in 1117 with Þorgils saga ok Hafliða. Other sagas included in the collection are Sturlu saga, Prestssaga Guðmundar Arasonar, Guðmundar saga biskups, Hrafns saga Sveinbjarnarsonar, Þórðar saga kakala, Svínfellinga saga and Íslendinga saga, composed by Sturla Þórðarson, which constitutes almost half of the compilation and covers the period 1183–1264. In some cases he broke up sagas to achieve chronological order. The compilation is often thought of as containing the main texts belonging to the textual corpus (or sub-genre) commonly referred to as the samtíðarsögur or 'contemporary sagas'. While it has been treated as a purely historical source, recent decades show acknowledgement that these are constructed texts representing a narrativised version of the past.
Sturlunga saga is the main source of Icelandic history during the 12th and 13th centuries and was written by people who experienced the internal power struggle which ended in Iceland's loss of sovereignty and submission to Norway in 1262–1264; the descriptions of wounds in Íslendinga saga are so detailed that they may be based on eyewitness accounts used in compensation claims. It is also indispensable for the details of social history which it contains. who may also have written Geirmundar þáttr and Haukdæla þáttr and possibly also Sturlu þáttr.