Cook, the son of a Scottish farm laborer, was born at Marston in England. He was educated at the local village school and joined the Royal Navy as an able seaman in 1755. He became a ship's master in 1759, spending eight years on survey work before being appointed by the Royal Society to take command of the Endeavour in 1768 on its voyage to the islands of Tahiti. He made two further major voyages of discovery in 1772–75 and in 1776.

In many ways Cook's journeys were the first modern voyages. His voyage in 1768 was to be the first of the great scientific expeditions that were to become so common in the following century. One of his main duties was to carry Royal Society observers to Tahiti to watch the transit of Venus across the Sun; such transits of planets were valuable for determining the distance between the Earth and the Sun. The scientists on board included the distinguished naturalists Joseph Banks and his assistant, Daniel Solander, and the expedition also carried artists to maintain a visual record.

The voyage's second main objective was to discover the southern continent, Terra Australis, which was believed to exist. It was assumed that the northern land mass of Eurasia must be symmetrically balanced by a southern land mass. Cook found New Zealand and extensively charted this over a period of six months and then, continuing his voyage, sighted the southeast coast of Australia on 19 April, 1770. He continued up the east coast of Australia successfully navigating the treacherous Great Barrier Reef. The Endeavour returned to England with a vast collection of scientific observations. Cook also won fame for preventing any of his crew members from dying of scurvy by insisting on a diet that included forms of fresh fruit and vegetables.

Cook led a second expedition (1772–75) to the South Seas in the Resolution and the Adventure in which he circumnavigated the high latitudes and traveled as far south as latitude 72°. He discovered new lands, including New Caledonia and the South Sandwich Islands, but found no trace of the ‘great southern continent’. It was also on the second voyage that the chronometer was used as a standard issue after its successful testing. Before 1772 navigators determined their longitude either by guesswork or by some very complicated calculations based on the Moon. Now, merely by noting the time and making comparatively simple calculations, it was possible to determine positions east or west of Greenwich. On his return he was made a fellow of the Royal Society and, for his paper on scurvy and its prevention, was awarded the Copley Medal.

Cook's third voyage (1776), again in the Resolution, ended in disaster. In trying to recover one of the ship's boats, which had been stolen by Polynesian islanders, Cook was attacked and killed by the natives on the beach of Kealakekua Bay.