James Cook was a British explorer known for his three significant voyages in the 18th century. His first voyage (1768-1771) aimed to observe the transit of Venus and led to the mapping of New Zealand and the eastern coast of Australia. On his second voyage (1772-1775), Cook sought to find the mythical southern continent, sailing further south than any previous explorer. His third voyage (1776-1779) focused on the Pacific, where he explored the Hawaiian Islands and attempted to find a northwest passage, ultimately leading to his death in Hawaii.