This chapter presents the geological features of the Jeju Island Geopark which was endorsed in 2010 and revalidated in 2014. Various volcanic geosites such as cinder cones, tuff cones, lava dome, lava tube caves and others are briefly explained. In addition, a Pleistocene fossil site together with a carbonate beach composed of Holocene carbonate algal nodules is also present in the geopark. This chapter also includes conservation and protection measures of the geosites and the monitoring which has been carried out since endorsement. Education and geotourism as well as various programs for sustainable development are also introduced.