Reiki (霊気^?, English pronunciation: /ˈreɪkiː/) is a spiritual practice developed in 1922 by Japanese Buddhist Mikao Usui. It uses a technique commonly called palm healing as a form of complementary and alternative medicine and is sometimes classified as oriental medicine by some professional bodies. Through the use of this technique, practitioners transfer healing energy in the form of ki through the palms.

There are two main branches of Reiki, commonly referred to as Traditional Japanese Reiki and Western Reiki. Within both Traditional and Westernised forms of Reiki, there are three forms of degrees, commonly referred to as the First, Second, and Master/Teacher degree. According to Reiki practitioners and Masters, at First Degree, a Reiki practitioner is able to heal himself and others, at Second Degree is able to heal others distantly (commonly called distant healing) with the use of specialised symbols, and at Master level (specifically Master/Teacher level) is able to teach and attune others to Reiki.

A 2008 systematic review of randomised clinical trials concluded that "..the evidence is insufficient to suggest that reiki is an effective treatment.." for the conditions studied (depression, pain and anxiety, and others).