Magnet therapy is a type of "alternative" medicine which claims that magnetic fields have healing powers. Some claim that magnets can help broken bones heal faster, Many civilizations throughout history have used magnets to treat illness. Ancient Egyptian priests and the fourth century Greek physician Hippocrates documented the use of magnets. The 15th century Swiss physician and chemist Paracelsus hypothesized that magnets may attract diseases out of the body.

In modern times, magnetic fields play an important role in Western medicine. For example, they are used in magnetic resonance imaging.

Some practitioners have theorized that magnet therapy may improve circulation, increase blood oxygen, alkalinize bodily fluids, decrease deposition of toxic materials in blood vessel walls (such as cholesterol plaques) or relax blood vessels through effects on cellular calcium channels. Other theories describe altered nerve impulses, reduced edema or fluid retention, increased endorphins, muscle relaxation, cell membrane effects or stimulation of acupoints. Some traditional Chinese medicine (TCM) practitioners suggest that magnets may affect patterns of flow of the body's life force, known as chi (qi). None of these theories has been adequately assessed by scientific research.