Maalox was a brand of antacid owned by Sanofi. Their main product is a flavored liquid containing a suspension of aluminum hydroxide and magnesium hydroxide, which act to neutralize or reduce stomach acid, for the purpose of relieving the symptoms of indigestion, heartburn, gastroesophageal reflux disease, and also stomach or duodenal ulcers. It also contains simethicone, an anti-foaming agent which helps eliminate bloating from gas. In large doses, the medicine can act as a laxative. The trademark is owned by Novartis International AG, and was first produced commercially in 1949.

The acronym ‘MAALOX’ refers to the solution’s compositional elements: MAgnesium and ALuminum as OXides. The oxides and hydroxides react with the hydrochloric acid in the stomach, neutralizing it.

Some may find certain Maalox medications, such as Maalox Multi-Action, to be a successful anti-diarrhea treatment due to the aluminum hydroxide content, which in normal situations has a tendency to result in constipation. Maalox may also be used to treat nausea and stomach cramps associated with dyspepsia, diarrhea, or constipation.

Maalox was developed in a collaboration between William H. Rorer, Inc., and a medical doctor and researcher specializing in gastrointestinal issues, Alison Howe Price from Philadelphia. The collaboration occurred after World War II when Claude Newhart, a salesman and pharmacist for the company, had an idea that he thought might change the company's fortunes. According to the Rorer family, he suggested that instead of selling pain relievers manufactured by others, they should create their own products. Gerald Rorer, then President of Rorer, told Newhart to "go and find something." Newhart took up the challenge and contacted an old acquaintance from his student days working at a Philadelphia drugstore, Martin H. Rehfuss, who happened to be chief of medicine at Thomas Jefferson Hospital. It was Rehfuss who introduced Newhart to Price. Soon thereafter, Newhart convinced Price to become a consultant for the Fort Washington, Pennsylvania based Willam H. Rorer, Inc. In the end, Maalox became the first product the partnership produced. Maalox eventually became the world's best selling antacid and forever changed the company's fortunes.

Liquid Maalox contains aluminum hydroxide, magnesium hydroxide, and simethicone.

Maalox Regular Strength chewable tablets contain 600 mg of calcium carbonate. Maalox Extra Strength + Anti-Gas tablets contain 1000 mg of calcium carbonate and 60 mg of simethicone.

Maalox is used to treat moderate dyspepsia, which includes symptoms of a burning sensation in the stomach or chest area, bloating, and/or gas pain, especially occurring after meals. It is used in combination with oxycodone to treat esophageal pain in cancer therapy patients. It is also a common component of a GI cocktail used in emergency rooms.

Maalox is used in scientific research to simulate for silt/mud/soil in water, along with other dissolved particulates. The particulate size exceeds 11 micrometres.