Educated as a physician, Gilbert settled in London and began to practice in 1573. His principal work, De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (1600; On the Magnet, Magnetic Bodies, and the Great Magnet of the Earth), gives a full account of his research on magnetic bodies and electrical attractions. After years of experiments he concluded that a compass needle points north–south and dips downward because the Earth acts as a bar magnet. The first to use the terms electric attraction, electric force, and magnetic pole, he is often considered the father of electrical studies.

In 1601 Gilbert was appointed physician to Queen Elizabeth I, and upon her death in 1603 was appointed physician to King James I. He left an unpublished work that was edited by his brother from two manuscripts and published posthumously in 1651 as De Mundo Nostro Sublunari Philosophia Nova (“A New Philosophy of Our Sublunar World”). He held modern views on the structure of the universe, agreeing with Copernicus that the Earth rotates on its axis. He concluded that fixed stars are not all the same distance from the Earth and believed that the planets were held in their orbits by a form of magnetism.