Mobile Bay is an inlet of the Gulf of Mexico, lying within the state of Alabama in the United States. Its mouth is formed by a peninsula on the eastern side and Dauphin Island, a barrier island on the western side. Rivers Mobile and Tensaw empty into the northern end of the bay. East Fowl River and Dog River empty into the Western side of the bay.

A famous naval battle of the Civil War was fought here.

The city of Mobile, Alabama, is situated at the head of the bay on the western shore. On the eastern shore of the bay are found several small communities, including Daphne, Fairhope, and Point Clear. In the summer the residents of the eastern and western shores sometimes enjoy the fruits of a mysterious natural phenomenon called a jubilee, when fish and crabs swarm toward shore and can be easily harvested by people wading in the shallows.

On August 5, 1864 during the American Civil War, Admiral David Farragut led a Union flotilla through Confederate defenses and sealed one of the last major Southern ports of the bay in the Battle of Mobile Bay.

On September 13, 1979, Hurricane Frederic entered the bay with winds reaching 145 mph, destroying the bridge to Dauphin Island.