Robert Were Fox (April 26, 1789 - July 25, 1877), English geologist and natural philosopher, was born at Falmouth.

He was a member of the Society of Friends, and was descended from members who had long settled in Cornwall, although he was not related to George Fox who had introduced the community into the county.

He was distinguished for his researches on the internal temperature of the earth, being the first to prove that the heat increased definitely with the depth; his observations being conducted in Cornish mines from 1815 for a period of forty years.

In 1829 he commenced a series of experiments on the artificial production of miniature metalliferous veins by means of the long-continued influence of electric currents, and his main results were published in Observations on Mineral Veins (Rep. Royal Cornwall Polytech. Soc., 1836).

He was one of the founders in 1833 of the Royal Cornwall Polytechnic Society. He constructed in 1834 an improved form of reflector clipping needle. In 1848 he was elected fellow of the Royal Society. His garden at Penjerrick near Falmouth became noted for the number of exotic plants which he had naturalized.

His daughter Caroline Fox was a noted diarist.

See A Catalogue of the Works of Robert Were Fox, F.R.S., with a Sketch of his Life, by JH Collins, 1878.