Enema, also known as clyster, is a fluid injected into the lower bowel by way of the rectum.

The most frequent use of an enema is to relieve constipation or for bowel cleansing before a medical examination or "procedure".  In standard medicine an enema may also be employed as a lower gastrointestinal series (also called a barium enema), to check diarrhea, as a vehicle for the administration of food, water or medicine, as a stimulant to the general system, as a local application and, more rarely, as a means of reducing temperature, as treatment for encopresis, and as a form of rehydration therapy (proctoclysis) in patients for whom intravenous therapy is not applicable.

Enemas are used as part of some alternative health therapies and are also used to administer drugs for recreational or religious reasons.