The son of William Banks of Revesby Abbey, Lincolnshire, Joseph Banks inherited a large fortune when he came of age, and later used this money to finance his scientific expeditions. Born in London, he studied botany at Oxford, graduating in 1763, and three years later traveled abroad for the first time as naturalist on a fishery-protection vessel heading for Labrador and Newfoundland. On the voyage he was able to collect many new species of plants and insects and, on his return, was elected a fellow of the Royal Society.

In London Banks learned that the Royal Society was organizing a voyage to the South Pacific to observe the transit of Venus across the Sun. In 1768 James Cook set sail in the Endeavour and Banks, together with a team of artists and the botanist Daniel Solander, accompanied him. Cook landed in Australia, a continent with a flora and fauna different from any found elsewhere. Banks found that most of the Australian mammals were marsupials, which are more primitive, in evolutionary terms, than the placental mammals of other continents.

After three years with the Endeavour Banks returned, with a large collection of unique specimens, to find himself famous. George III, interested in hearing a first-hand account of Banks's travels, invited him to Windsor. This visit was the start of a long friendship with the king, which helped Banks establish many influential contacts – possibly a factor in his election as president of the Royal Society in 1778, a post that he held until his death.

Throughout his life Banks retained his interest in natural history and in the specimens collected on the many expeditions mounted during that period. As honorary director of Kew Gardens he played a major part in establishing living representatives of as many species as possible at Kew and in providing a center for advice on the practical use of plants. He initiated many successful projects, including the introduction of the tea plant to India from its native China and the transport of the breadfruit from Tahiti to the West Indies. By George III's request, he also played an active role in importing merino sheep into Britain from Spain.

The British Museum (Natural History) now houses Banks's library and herbarium, both regarded as major collections.