Gastroenterology (from the Greek gastḗr- "belly", -énteron "intestine", and -logía "study of") is the branch of medicine focused on the digestive system and its disorders. The digestive system consists of the gastrointestinal tract, sometimes referred to as the GI tract, which includes the esophagus, stomach, small intestine and large intestine as well as the accessory organs of digestion which include the pancreas, gallbladder, and liver.

The digestive system functions to move material through the GI tract via peristalsis, break down that material via digestion, absorb nutrients for use throughout the body, and remove waste from the body via defecation. Physicians who specialize in the medical specialty of gastroenterology are called gastroenterologists or sometimes GI doctors.

Some of the most common conditions managed by gastroenterologists include gastroesophageal reflux disease, gastrointestinal bleeding, irritable bowel syndrome, inflammatory bowel disease (IBD) which includes Crohn's disease and ulcerative colitis, peptic ulcer disease, gallbladder and biliary tract disease, hepatitis, pancreatitis, colitis, colon polyps and cancer, nutritional problems, and many more.

Citing from Egyptian papyri, John F. Nunn identified significant knowledge of gastrointestinal diseases among practicing physicians during the periods of the pharaohs. Irynakhty, of the tenth dynasty, c. 2125 B.C., was a court physician specializing in gastroenterology, sleeping, and proctology.

Among ancient Greeks, Hippocrates attributed digestion to concoction^{[disambiguation needed]}. Galen's concept of the stomach having four faculties was widely accepted up to modernity in the seventeenth century.

1. International Classification of Disease (ICD 2007)/WHO classification:

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3. National Library of Medicine Catalogue (NLM classification 2006):