The following narrative is not so much a story as a biography. My hero is not an imaginary one; he was a real flesh and blood man who reigned as King of Norway just nine centuries ago. The main facts of his adventurous career--his boyhood of slavery in Esthonia, his life at the court of King Valdemar, his wanderings as a viking, the many battles he fought, his conversion to Christianity in England, and his ultimate return to his native land--are set forth in the various Icelandic sagas dealing with the period in which he lived. I have made free use of these old time records, and have added only such probable incidents as were necessary to give a continuous thread of interest to the narrative. These sagas, like the epics of Homer, were handed down from generation to generation by word of mouth, and they were not committed to writing until a long time after Olaf Triggvison's death, so that it is not easy to discriminate between the actual facts as they occurred and the mere exaggerated traditions which must surely have been added to the story of his life as it was told by the old saga men at their winter firesides. But in most instances the records corroborate each other very exactly, and it may be taken that the leading incidents of the story are historically true.