<p>Mont-Saint-Michel is one of the most iconic sites in the world. It receives over 3&#xa0;million visitors a year, and has been featured in artwork, books, films, television shows, and video games. This paper examines its geoheritage as well as related geosites. These include Mont-Saint-Michel Bay; Tombelaine, a small island situated several kilometers north of Mont-Saint-Michel; Mont-Dol, which is, like Mont-Saint-Michel, a granite tumulus, with significant links to the monastery; and Gargano (eastern Italy), the site of the oldest shrine dedicated to St. Michael, the archangel, and the probable location of an earthquake in the early 5th century AD. The study utilizes the methods of geomythology, a hybrid discipline that combines geology and mythology to glean scientific information from legends and stories. The study also engages a field related to geomythology, that is, hydromythology, as well as insights from paleoseismology, landscape mythology, paleontology, osteology, and even psychiatry, thereby shedding light on the site’s cultural and natural riches, and on the life and “afterlife” of its founder, Bishop Aubert of Avranches.</p>