Cape Darnley is the ice-covered cape forming the northern extremity of Bjerkø Peninsula at the west side of MacKenzie Bay. On December 26, 1929, Sir Douglas Mawson, from the masthead of the RRS Discovery while at 66°57′S 71°57′E / 66.950°S 71.950°E, saw land miraged up on the southwest horizon. On February 10, 1931, he returned in the Discovery and was able to approach close enough to see the headland, naming it for E.R. Darnley, Chairman of the Discovery Committee of the Colonial Office, London, 1923 to 1933.