Shackleton is most noteworthy for leading the unsuccessful Imperial Trans-Antarctic Expedition, often known as the "Endurance Expedition", between 1914 and 1916.

Although Shackleton failed to achieve his goal of crossing the Antarctic continent on foot, he demonstrated the qualities of leadership for which he is best remembered when the expedition ship Endurance became trapped in the ice and was destroyed.

Shackleton, known by his contemporaries as "the Boss", led his men to refuge on Elephant Island before heading across 800 miles (1,300 km) of the Southern Ocean to South Georgia, in an open boat with five other men. Upon reaching the remote island, Shackleton and two others crossed severe, mountainous terrain to reach a whaling station, from which he was able eventually to rescue his men on Elephant Island. All the men on Endurance survived their ordeal after spending 22 months in the Antarctic, although three men of the supporting Ross Sea Party lost their lives.

Shackleton was a key figure in the Heroic Age of Antarctic Exploration alongside Roald Amundsen, Douglas Mawson, and Robert Falcon Scott, each of whom is famed for exploits that captured the public imagination. In recent times, he has become known for his leadership skills, and is the topic of many books and films that focus on the explorer's ability to lead men through challenging conditions.