William Henry Eccles FRS[1] (23 August 1875 – 29 April 1966) was a British physicist and a pioneer in the development of radio communication.

Eccles was an advocate of Oliver Heaviside's theory that a conducting layer of the upper atmosphere could reflect radio waves around the curvature of the Earth, thus enabling their transmission over long distances.

In 1912 Eccles suggested that solar radiation was responsible for the observed differences in radio wave propagation during the day and night.

Eccles invented the term diode to describe an evacuated glass tube containing two electrodes; an anode and a cathode.

He helped in the design of the first long wave radio station, and became involved in the early work of the British Broadcasting Company (later the BBC) following its establishment in 1922.