Roundtop Mountain is a stratovolcano located on the Aleutian island of Unimak in the U.S. state of Alaska. Its last eruption was sometime between 9,100 and 10,000 years ago. This geographic feature was first called Dome in 1897 by Lieutenant Commander J. F. Moser, of the U.S. Navy. Its name was reported as Round Top by the U.S. Coast and Geodetic Survey in 1902. Isanotski Peaks, the nearest higher neighbor, is positioned to the west-southwest.