Robert Fludd, also known as Robertus de Fluctibus (1574, Bearsted, Kent - September 8 1637, London) was a prominent English Rosicrucian and Paracelsian physicist, astrologer, and mystic. He was the son of Sir Thomas Fludd , a high-ranking governmental official.

Between 1598 and 1604, Fludd studied medicine, chemistry and the occult on the European mainland, but he is best known for his research in occult philosophy. He had a celebrated exchange of views with Johannes Kepler concerning the scientific and hermetic approaches to knowledge.

In 1630, Fludd proposed many perpetual motion machines. People were trying to patent variations of Fludd's machine in the 1870s. Fludd's machine worked by recirculation by means of a water wheel and Archimedean screw. The device pumps the water back into its own supply tank. _{[1] [2]}

He is a descendant of Cunedda Wledig ap Edern, King of Gwynedd, which in now part of Wales.