Carsten Egeberg Borchgrevink (1 December 1864 – 21 April 1934) was a Norwegian polar explorer and a pioneer of Antarctic travel. He inspired Sir Robert Falcon Scott, Sir Ernest Shackleton, Roald Amundsen, and others associated with the Heroic Age of Antarctic Exploration.

Borchgrevink was born and raised in Christiania (now Oslo) as the son of a Norwegian lawyer and an English-born immigrant mother. He began his exploring career in 1894 by joining a Norwegian whaling expedition, during which he became one of the first people to set foot on the Antarctic mainland. This achievement helped him to obtain backing for his Southern Cross expedition, which became the first to overwinter on the Antarctic mainland, and the first to visit the Great Ice Barrier since the expedition of Sir James Clark Ross nearly sixty years earlier.

The expedition's successes were received with only moderate interest by the public – and by the British geographical establishment, whose attention was by then focused on Scott's upcoming Discovery expedition. Some of Borchgrevink's colleagues were critical of his leadership, and his own accounts of the expedition were regarded as journalistic and unreliable.

From 1898 to 1900, Borchgrevink led the British-financed Southern Cross expedition. He was one of three scientists in 1902 to report on the aftermath of the Mount Pelée eruption. Thereafter he returned to Kristiania, leading a life mainly away from public attention. His pioneering work was subsequently recognised and honoured by several countries, and in 1912 he received a tribute from Roald Amundsen, leader of the first expedition to reach the South Pole.

In 1930 the Royal Geographical Society acknowledged Borchgrevink's contribution to polar exploration and awarded him its Patron's Medal. The Society acknowledged in its citation that justice had not previously been done to the work of the Southern Cross expedition.