A high island is, in geology (and sometimes in archaeology), an island of volcanic origin. The term is used to distinguish such islands from low islands, whose origin is due to sedimentation or uplifting of coral reefs.

This distinction is important to understand, as there are a number of "high islands" which rise no more than a few feet above sea level, often classified as "rocks", while some "low islands", such as Makatea , Nauru, Niue and Banaba, rise several hundred feet above sea level.

The two types of islands are often found in close proximity, especially among the islands of the South Pacific Ocean, where low islands are found on the fringing reefs which surround most high islands.