Ōyamazumi Shrine is a Shinto shrine located on the island of Ōmishima in the Seto Inland Sea. Administratively, it is part of the city of Imabari, Ehime Prefecture. It was the ichinomiya shrine of former Iyo Province. The main festival of the shrine is held annually on the April 22 by the lunar calendar.

Iyo Province was a province of Japan in the area of northwestern Shikoku. Iyo bordered on Sanuki Province to the northeast, Awa to the east, and Tosa to the south. Its abbreviated form name was Yoshū (予州). In terms of the Gokishichidō system, Iyo was one of the provinces of the Nankaidō circuit. Under the Engishiki classification system, Iyo was ranked as one of the "upper countries" (上国) in terms of importance, and one of the "far countries" (遠国) in terms of distance from the capital. The provincial capital was located in what is now the city of Imabari, but its exact location is still unknown. The ichinomiya of the province is the Ōyamazumi Shrine located on the island of Ōmishima in what is now part of Imabari. The people spoke Iyo dialect.