Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases in which stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/or complications. Symptoms include dental corrosion, dysphagia, heartburn, odynophagia, regurgitation, non-cardiac chest pain, extraesophageal symptoms such as chronic cough, hoarseness, reflux-induced laryngitis, or asthma. In the long term, and when not treated, complications such as esophagitis, esophageal stricture, and Barrett's esophagus may arise.

Risk factors include obesity, pregnancy, smoking, hiatal hernia, and taking certain medications. Medications that may cause or worsen the disease include benzodiazepines, calcium channel blockers, tricyclic antidepressants, NSAIDs, and certain asthma medicines. Acid reflux is due to poor closure of the lower esophageal sphincter, which is at the junction between the stomach and the esophagus. Diagnosis among those who do not improve with simpler measures may involve gastroscopy, upper GI series, esophageal pH monitoring, or esophageal manometry.

Treatment options include lifestyle changes, medications, and sometimes surgery for those who do not improve with the first two measures. Lifestyle changes include not lying down for three hours after eating, lying down on the left side, raising the pillow or bedhead height, losing weight, and stopping smoking. Foods that may precipitate GERD symptoms include coffee, alcohol, chocolate, fatty foods, acidic foods, and spicy foods. Medications include antacids, H₂ receptor blockers, proton pump inhibitors, and prokinetics.

In the Western world, between 10 and 20% of the population is affected by GERD. It is highly prevalent in North America with 18% to 28% of the population suffering from the condition. Occasional gastroesophageal reflux without troublesome symptoms or complications is even more common. The classic symptoms of GERD were first described in 1925, when Friedenwald and Feldman commented on heartburn and its possible relationship to a hiatal hernia. In 1934 gastroenterologist Asher Winkelstein described reflux and attributed the symptoms to stomach acid.