Biloxi ( bih-LUK-see; French: [bilusi]) is a city in Harrison County, Mississippi, United States. It lies on the Gulf Coast in southern Mississippi, bordering the city of Gulfport to its west. The adjacent cities are both designated as seats of Harrison County. The population of Biloxi was 49,449 at the 2020 census, making it the state's 4th most populous city. It is a principal city of the Gulfport–Biloxi metropolitan area, home to 416,259 residents in 2020. The area's first European settlers were French colonists. The beachfront of Biloxi lies directly on the Mississippi Sound, with barrier islands scattered off the coast and into the Gulf of Mexico. Keesler Air Force Base lies within the city and is home to the 81st Training Wing and the 403d Wing of the U.S. Air Force Reserve.