Sør Rondane Mountains
Isachsen Mountain is a large mountain rising to , standing southeast of Mount Bergersen in the Sør Rondane Mountains of Antarctica. It was mapped by Norwegian cartographers in 1957 from air photos taken by U.S. Navy Operation Highjump, 1946–47, and named for Major Gunnar Isachsen, the leader with Captain Hjalmar Riiser-Larsen of the Norwegian expedition 1930–31.