Helgeseter Priory or Elgeseter Priory was a house of Augustinian Canons in what is now Elgeseter in Trondheim, Norway, across the river Nidelven from Nidaros Cathedral. The priory was connected to the cathedral by Elgeseter Bridge, making it possible for the canons to perform their duty in the cathedral choir. The monastery was founded by Archbishop Eystein no later than 1183, and rapidly assumed political importance.
In May 1240 Duke Skule was killed outside this monastery. He had been attacked by the Birkebeiners in Nidaros, and after wandering for a couple of days took refuge in Helgeseter. The Birkebeiners set fire to the monastery and forced Skule out again, whereupon they killed him, with his son Peter.
In 1564 the buildings were burned down and after 1606 the site was used as a quarry. There are now no visible ruins, but underground remains lie beneath the present Klostergata 47 and 60-62 and the roadway between them, a little south of the Nidelven.
- Lunde, 0. (1977): Trondheims fortid i bygrunnen. Riksantikvarens skrifter, nr. 2, pp. 145-148 and 215. Trondheim. (Norwegian)