Australia has long held activities, interests, ambitions, and visions related to Antarctica and the Great Southern Ocean, dating back to colonial times. These aspirations arguably precipitated federation and underpinned a vision of empire extending from the equator to the South Pole—across two continents, three oceans, and multiple islands— as framed by Rohan Howitt in his book The Southern Ocean: Australia, Antarctica and Empire (Melbourne University Press, 2025). We discuss this nineteenth-century vision, which, although now largely forgotten, leaves a legacy that includes Australia’s claim to sovereignty over 42% of the Antarctic continent. It also highlights Australia's role as a signatory to the remarkable and unique Antarctic Treaty among twelve nations, at a time of increasing geopolitical tensions and contested claims.