Aeneas Lionel Acton Mackintosh (1 July 1879 – 8 May 1916) 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.