The Mississippi Sound is a sound along the Gulf Coast of the United States. It runs east-west along the southern coasts of Mississippi and Alabama, from the mouth of the Pearl River at the Mississippi-Louisiana state border to the Dauphin Island Bridge, a distance of about 90 miles (145 km). The sound is separated from the Gulf on its southern side by the Mississippi–Alabama barrier islands: Cat, Ship, Horn, West Petit Bois, Petit Bois, and Dauphin. Ship, Horn, West Petit Bois and Petit Bois Islands are part of the National Park Service's Gulf Islands National Seashore. Those islands separate the sound from the Gulf of Mexico. The sediment of the islands was created partly by the ancient Mississippi River when the St. Bernard Lobe of the Mississippi Delta was active over two thousand years ago. The expansion of the St. Bernard subdelta slowly isolated the Mississippi Sound from ocean dynamics of the open Gulf of Mexico.

Gulfport is the second-most populous city in the U.S. state of Mississippi after the state capital, Jackson. Along with Biloxi, Gulfport is the co-county seat of Harrison County and part of the Gulfport–Biloxi metropolitan area. As of the 2020 census, Gulfport has a population of 72,926; the metro area has a population of 416,259. Gulfport lies along the gulf coast of the United States in southern Mississippi, taking its name from its port on the Gulf Coast on the Mississippi Sound. It is home to the U.S. Navy Atlantic Fleet Seabees.