Gilliamsen Peak (71°51′S70°20′W) is a peak (about 650 m) marking the southeast extremity of the Staccato Peaks in the south portion of Alexander Island, Antarctica. The peak was photographed from the air by Lincoln Ellsworth in 1935. Named by Advisory Committee on Antarctic Names (US-ACAN) after Lieutenant Commander Donald A. Gilliamsen, U.S.