Mount Iō also Mount Iwo is a volcano in the Akan Volcanic Complex of Hokkaidō, Japan. It sits within the borders of the town of Teshikaga.
The mountain was once mined for sulphur, hence its name. To the Ainu the mountain was known as Atosanupuri. The mountain is quite bare. Despite its bareness and being a rather low mountain at 508 metres it hosts alpine plant life. It hosts colonies of Siberian Dwarf Pine, Rhododendron diversipilosum, and other members of Ericaceae.