This work is now lost but it is believed to have been an expansion of the Latin Óláfs saga Tryggvasonar written by his monastic brother, Oddr Snorrason.
In the 1190s, two sagas of Olaf Tryggvason were written in Iceland, by Oddr Snorrason and Gunnlaugr Leifsson.
Composed around 1300 it takes Óláfs saga Tryggvasonar in Snorri Sturluson's Heimskringla as its base but expands the narrative greatly with content from the previous biographies of the king by Oddr Snorrason and Gunnlaugr Leifsson as well as less directly related material.