Bluff Island is an island lying 1 kilometre (0.5 nmi) south of Magnetic Island and 4 kilometres (2 nmi) west of the Breidnes Peninsula, Vestfold Hills, in Prydz Bay, Antarctica. It was mapped from aerial photos taken by the Lars Christensen Expedition, 1936–37, re-emapped by the Australian National Antarctic Research Expeditions (1957–58) and so named because the south end of the island is marked by a steep cliff face.