Aeneas Lionel Acton Mackintosh was a British Merchant Navy officer and Antarctic explorer who commanded the Ross Sea party as part of Sir Ernest Shackleton's Imperial Trans-Antarctic Expedition, 1914–1917. The Ross Sea party's mission was to support Shackleton's proposed transcontinental march by laying supply depots along the latter stages of the march's intended route. In the face of persistent setbacks and practical difficulties, Mackintosh's party fulfilled its task, although he and two others died in the course of their duties. Mackintosh's first Antarctic experience was as second officer on Shackleton's Nimrod expedition, 1907–1909. Shortly after his arrival in the Antarctic, a shipboard accident destroyed his right eye, and he was sent back to New Zealand. He returned in 1909 to participate in the later stages of the expedition; his will and determination in adversity impressed Shackleton, and led to his Ross Sea party appointment in 1914.

The history of Antarctica emerges from early Western theories of a vast continent, known as Terra Australis, believed to exist in the far south of the globe. The term Antarctic, referring to the opposite of the Arctic Circle, was coined by Marinus of Tyre in the 2nd century AD.