The island's highest peak is Washigatozan (鷲ヶ頭山) at an altitude of 437 m (1,434 ft).

[1] Ōmishima is kidney-shaped and together with Ōsakikamijima on the west encloses the calm bay of Utena, where the primary seaport of Miyaura [ja] is located.

The island's Utena Dam reservoir is the primary freshwater source for Ōmishima itself and the nearby Hakata.

Ōmishima is connected to the mainland of Honshu and Shikoku islands by the bridges of the Nishiseto Expressway (Shimanami Kaidō).

This Ehime Prefecture location article is a stub.