Bay St. Louis is a city located on the Gulf Coast in the state of Mississippi, United States. It serves as the county seat of Hancock County and is situated on the west side of the Bay of St. Louis. The city is part of the larger Gulfport-Biloxi metropolitan area.
According to the 2020 census, the population of Bay St. Louis was 9,284, reflecting a slight increase from the 9,260 residents recorded in the 2010 census.