Olaf II Haraldsson, also Olav Haraldsson, later known as Saint Olaf and Olaf the Holy, was King of Norway from 1015 to 1028. Son of Harald Grenske, a petty king in Vestfold, Norway, he was posthumously given the title Rex Perpetuus Norvegiae and canonised at Nidaros (Trondheim) by Bishop Grimketel, one year after his death in the Battle of Stiklestad on 29 July 1030. His remains were enshrined in Nidaros Cathedral, built over his burial site. His sainthood encouraged the widespread adoption of Christianity by Scandinavia's Vikings/Norsemen.

Nidaros, Niðarós or Niðaróss was the medieval name of Trondheim when it was the capital of Norway's first Christian kings. It was named for its position at the mouth of the River Nid.