Radiesthesia is the ability to detect "radiation" within the human body. According to the theory, all human bodies give off unique or characteristic "radiations" as do all other physical bodies or objects.

A practitioner of Radiestheisa believes in his or her ability to detect the interplay of these radiations. Thus radiesthesia is cited as the explanation of such phenomena as dowsing by rods and pendulums in order to locate buried substances, diagnose illnesses.

The term Radiesthesia first entered English in the 1930s and was borrowed from the earlier French radiésthesie. The English word is a compound of the prefix radi(o)-, referring to radiation and the rare term aesthesia meaning "perception by the senses", or "the capacity for feeling or sensation", which comes from the ancient Greek aisthesis "a perceiving".