Heimskringla is a collection of sagas about the Norwegian kings, beginning with the saga of the legendary Swedish dynasty of the Ynglings, followed by accounts of historical Norwegian rulers from Harald Fairhair of the 9th century up to the death of the pretender Eystein Meyla in 1177. It was written by Snorri Sturluson ca. 1230.
Available at Project Gutenberg: Heimskringla