Through its origins, acupuncture has been embedded in the concepts of Traditional Chinese medicine (TCM). Its general theory is based on the premise that bodily functions are regulated by the flow of an energy-like entity called qi. Acupuncture aims to correct imbalances in the flow of qi by stimulation of anatomical locations on or under the skin called acupuncture points, most of which are connected by channels known as meridians. Scientific research has not found any physical or biological correlate of qi, meridians and acupuncture points, and some contemporary practitioners needle the body without using a theoretical framework, instead selecting points based on their tenderness to pressure.

The earliest written record of acupuncture is found in the Huangdi Neijing (黄帝内经; translated as The Yellow Emperor's Inner Canon), dated approximately 200 BCE. The practice of acupuncture expanded out of China into the areas now part of Japan, Korea and Taiwan, diverging from the narrower theory and practice of mainland TCM in the process. A large number of contemporary practitioners outside of China follow these non-TCM practices, particularly in Europe.

Proponents of acupuncture believe that it promotes general health, relieves pain, treats infertility, treats and prevents disease. Scientific research has not found it effective for anything but the relief of some types of pain and nausea. Systemic reviews have found conflicting results regarding the prevention of postoperative nausea and vomiting though a 2009 Cochrane review concluded stimulation of the P6 acupuncture point was as effective as antiemetic medications. Acupuncture also appears to have a small effect in the short-term management of some types of pain though a 2011 review of review articles concluded that acupuncture was of doubtful efficacy in treating pain other than neck pain. It has been suggested that the positive results reported for acupuncture can be explained by placebo effects and publication bias and researchers have pointed out the difficulty in designing an adequate scientific control for any placebo effect acupuncture might have due to its invasiveness. The development and inclusion of retracting needles as a form of placebo control has resulted in a much larger number of studies concluding acupuncture's effects are due to placebo.