Latin lives of Óláfr Tryggvason were written by Oddr Snorrason and by Gunnlaugr Leifsson; both are now lost, but are thought to have formed the basis of Old Norse sagas on his life including in the collection of texts referred to as Heimskringla by scholars.
[1] Oddr made use of previous written works including those of Sæmundr fróði and Ari Þorgilsson as well as Acta sanctorum in Selio and possibly Historia de Antiquitate Regum Norwagiensium.
[2] It is difficult to tell how closely the translation reflects the Latin original, but it clearly owes a debt to hagiography, presenting King Óláfr as the apostle to the Norwegians.
It contains detail on Óláfr's conversion to Christianity and of his efforts to convert Norway, including many stories, among them that of the skald Hallfreðr vandræðaskáld.
The writer included from Oddr's account that Óláfr did not die at the Battle of Svolder, but lived to present King Ethelred of England with a book recounting his life and that of seven "other saints".