Egill's Saga or Egil's saga (Old Norse: Egils saga [ˈeɣels ˈsɑɣɑ]; Icelandic pronunciation: [ˈeijɪls ˈsaːɣa] ^ⓘ) is an Icelandic saga (family saga) on the lives of the clan of Egill Skallagrímsson (Anglicised as Egill Skallagrimsson), an Icelandic farmer, viking and skald. The saga spans the years c. 850–1000 and traces the family's history from Egill's grandfather to his offspring.

Its oldest manuscript (a fragment) dates back to c. 1250 AD. The saga comprises the sole source of information on the exploits of Egill, whose life is not historically recorded. Stylistic and other similarities between Egill's Saga and Heimskringla have led many scholars to believe that they were the work of the same author, Snorri Sturluson. The work is generally referred to as Egla [ˈɛkla] by Icelandic scholars.

The saga begins in Norway around 850, with the life of Egill's grandfather Ulf (Úlfr) aka Kveldulf or "Evening Wolf", and his two sons Thorolf (Þórólfr) and Skallagrim (Skalla-Grímr). Strife with the royal house drive the family out of the country, and they settle in Iceland. The brothers Egill and Thorolf Skallagrimsson are born. They have a tenuous tenure in Norway, but Egill is outlawed and they roam Scandinavia and serve the king of England. Egill tries to reclaim property back in Norway (as his wife's inheritance), but this is blocked, and Egill develops a personal vendetta against the King.

There are also vivid descriptions of his other fights and friendships, his relationship with his family (highlighted by his jealousy, as well as fondness for his older brother Thorolf), his old age, and the fate of his own son Thorstein (Þorsteinn, who was baptized once Roman Catholicism came to Iceland) and his children, who had many children of their own. The saga ends around the year 1000 and spans many generations.

Ulf (Kveldulf) had Hallbjorn Halftroll as his maternal uncle, and was known for his surpassing size and strength. He had accrued land and property from viking raids, and was a man of wisdom. He earned the nickname Kveldulf (Kveldúlfr, "Evening Wolf") because of his erratic temper at nightfall, and reputation for manifesting the so-called "shape-shifter" (hamrammr) abilities, explained in later chapters to be comparable (or equatable) with berserk fury. Extreme personal traits like these are manifested by his son Skallagrim and his grandson Egill as well.

King Harald Fairhair (Haraldr Hárfagri) was warring to unite all of Norway. Kveldulf refused to assist the local king of Fjordane, but rebuffed Harald's overtures as well, incurring his wrath. A compromise was mediated by Olvir Hnufa (Ölvir hnúfa or "Olvir Hump"), Kveldulf's brother-in-law and Harald's court poet: Kveldulf was to send his elder son Thorolf, as soon as he returned from viking expedition. Thorolf served the king well, but suspicion fell on him due to his becoming overly successful, exacerbated by words of slanderers. Thorolf was killed by the king who led a band of warriors, and the rift would force Skallagrim and his father Kveldulf to flee Norway to settle in Iceland.

Skallagrim journeyed to Harald's court seeking compensation for the death of his brother Thorolf, but offended the king and had to make a hasty exit empty-handed. Skallagrim and Kveldulf then recaptured a boat that had been seized from Thorolf, and after killing everyone on board, sent a taunting poem to the King. In the battle, Kveldulf displayed his "frenzy" (hamrammr or hamremi), which left him severely weakened. When the family emigrated to Iceland, Kveldulf did not survive the trip, and his coffin was set adrift. Near the spot where the coffin washed ashore in Iceland, Skallagrim established his settlement, which he named Borg. He took up a peaceful livelihood as a farmer and blacksmith, and raised his sons, Thorolf (named Þórólfr after his slain brother), and Egill (the titular hero).

The saga then proceeds to describe the lives of Thorolf and Egill Skallagrimsson, born in Iceland, and eventually making their way to Norway in adulthood. Thorolf visited Skallagrim's old friend in Norway, Thorir the Hersir (Þórir Hróaldsson). Here Thorolf befriended Prince Eirik Bloodaxe, Harald's favorite son and Thorir's fosterling. He approached the prince with a gift of a painted warship that Eirik was admiring, on advice of Bjorn (Björn Brynjólfsson), Thorir's brother-in-law.