邓肯半岛是南极洲的半岛，位于玛丽伯德地，处于卡尼岛东部，长56公里，美国地质调查局根据该国海军的空中照片绘入地图，现时由南极条约体系管理。

Duncan Peninsula (73°56′S 119°30′W / 73.933°S 119.500°W / -73.933; -119.500) is an ice-covered peninsula, 30 nautical miles (56 km) long, which forms the eastern part of Carney Island, along the coast of Marie Byrd Land. It was delineated from aerial photographs taken by U.S. Navy Operation Highjump in January 1947, and was named by the Advisory Committee on Antarctic Names for Admiral Donald B. Duncan, U.S. Navy, Vice Chief of Naval Operations under Admiral Robert Carney during the International Geophysical Year period of 1957–58.