Belching (also called burping and eructation) is the audible release of gas from the upper gastrointestinal tract (esophagus and stomach) of humans, and other animals into the pharynx, and usually out through the mouth.

In humans, belching can be caused by normal eating processes, or as a side effect of other medical conditions. When belching is excessive it may be classed as a belching disorder, one of the gastroduodenal disorders. Belching is a frequent symptom of gastroesophageal reflux disease (GERD) but this is distinct from a belching disorder.

There is a range of levels of social acceptance for burping: within certain contexts and cultures, burping is acceptable. In some cultures and situations it may even be perceived as humorous, while in others it is seen as impolite or even offensive and therefore unacceptable. An infant often accumulates gas when feeding, and this needs to be vented by way of burping. To burp the baby is the common expression.

Belching is also very common among other mammals. In particular, burping by domesticated ruminants, such as cows or sheep, is a major contributor of methane emissions and may have a negative effect on the environment. Significant research is being done to find mitigation strategies for ruminant burping, such as by modifying the animals' diets with Asparagopsis taxiformis, a type of red algae.

The belch reflex is responsible for the ability to belch. Most of the air that is swallowed during eating and drinking cannot be absorbed in the gastrointestinal tract and is vented by way of belching. Swallowed air is allowed to rise from the stomach into the esophagus, through a relaxed lower esophageal sphincter. The gaseous distention of the esophagus triggers the belch reflex in the relaxation and opening of the upper esophageal sphincter to release the air into the pharynx.

The expelled gas is mainly a mixture of the main components of atmospheric air - oxygen and nitrogen. Burps can be caused by drinking beverages such as beer and carbonated drinks, and in these cases, the expelled gas is mainly carbon dioxide.

Chewing gum, sucking on hard candy, talking while eating or drinking, or while smoking, can also cause more air to be swallowed and therefore increased belching. Also swallowing air may in some people be a nervous habit.

Belching can also be a symptom of disorders that cause indigestion such as a hiatal hernia, gastritis, gastroesophageal reflux disease (GERD), an ulcer, infection with H. pylori, gallbladder disease, and food allergies.