is an unincorporated community and census-designated place in Mobile County, Alabama, United States. It is included in the Mobile metropolitan statistical area. At the 2000 census the population was 3,918.
According to the U.S. Census Bureau, the community has a total area of 8.7 square miles (22.5 km²), of which, 8.7 square miles (22.4 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.34%) is water.
While the Northern and Eastern borders of Grand Bay are rather flexibly defined, both the Southern and Western edges of town are clearer, because Grand Bay extends to the state line on the west and the Gulf of Mexico on the South (although technically westernmost residents who consider themselves to live in Grand Bay may even stretch just over the state line into Mississippi).