Reiki (霊気, /ˈreɪkiː/) is a form of alternative medicine called energy healing. Reiki practitioners use a technique called palm healing or hands-on healing through which a "universal energy" is said to be transferred through the palms of the practitioner to the patient in order to encourage emotional or physical healing.

Reiki is a pseudoscience,[1] and is used as an illustrative example of pseudoscience in scholarly texts and academic journal articles. It is based on qi ("chi"), which practitioners say is a universal life force, although there is no empirical evidence that such a life force exists.[2][3] Clinical research has not shown reiki to be effective as a treatment for any medical condition.[2] There has been no proof of the effectiveness of reiki therapy compared to placebo. An overview of reiki investigations found that studies reporting positive effects had methodological flaws. The American Cancer Society stated that reiki should not replace conventional cancer treatment,[4] a sentiment echoed by Cancer Research UK[5] and the National Center for Complementary and Integrative Health.[6]

Developed in Japan in 1922 by Mikao Usui,[1][7] it has been adapted into varying cultural traditions across the world.