Mount Sidley is the highest dormant volcano in Antarctica, a member of the Volcanic Seven Summits, with a summit elevation of . It is a massive, mainly snow-covered shield volcano which is the highest and most imposing of the five volcanic mountains that comprise the Executive Committee Range of Marie Byrd Land. The feature is marked by a spectacular 5 km wide caldera on the southern side and stands NE of Mount Waesche in the southern part of the range.