Biloxi is located in southeastern Harrison County, bordered to the south by Mississippi Sound (part of the Gulf of Mexico) and to the northeast partially by Biloxi Bay, which forms part of the Jackson County line.

Biloxi's main highway is U.S. Highway 90 (Beach Boulevard), which runs along the beach and by the casinos. It connects the city to Gulfport and points westward and to Ocean Springs and Pascagoula to the east.

In the center of what fisheries biologists' term "The Fertile Fisheries Crescent", Biloxi offers some of the finest sportfishing along the entire northern coast of the Gulf of Mexico. Spotted seatrout, red drum, Spanish and king mackerel, flounder, snapper, grouper, sharks, and more are all available to anglers during the fishing season. It is not known how Hurricane Katrina affected this ecosystem.

Bay St. Louis is the county seat of Hancock County. Located on the Gulf Coast on the west side of the Bay of St. Louis. It is situated on west side of the Bay of St. Louis, which empties into the Mississippi Sound. The city is bordered to the north by the Jourdan River, the primary inlet of the bay. The eastern border of the city is the Harrison County line in the middle of the bay.

Pass Christian, nicknamed The Pass, is in Harrison County.  Geographically, the town of Pass Christian is located on the Mississippi Sound, and is situated on a peninsula, with water on three sides: the Gulf of Mexico to the south, the Bay of St. Louis to the west and a long stretch of bayou to the north. The unincorporated area north of the bayou, known as DeLisle, shares a zip code with Pass Christian, but is not within the city limits. DeLisle was formerly known as Wolf Town or Wolftown.

Diamondhead is located just over 50 miles northeast of New Orleans, Louisiana.  In February 2012, Diamondhead was officially incorporated as a city. Unlike most of the Mississippi Gulf Coast, which is relatively level, the Diamondhead area has more rolling topography, with elevations ranging from sea level to over 100 feet. The city is bordered to the south by the Bay of Saint Louis. Rotten Bayou runs west and northwest of the city. Harrison County borders Diamondhead to the east.

Kiln is an unincorporated community in Hancock County. The town is located about 50 miles northeast of New Orleans, Louisiana. Kiln is referred to locally as "the Kiln", with the "n" silent. This pronunciation is in accordance with the pronunciation of the word "kiln" during the Middle English Period. The Jourdan River borders the town to the south. Bayou Coco is in the southeastern part of the town, and Bayou Talla flows through the southern part of the community into the Jourdan. Bayou La Terre borders Kiln to the east. 

Waveland is in southeastern Hancock County along the shore of Mississippi Sound, an embayment of the Gulf of Mexico. It is bordered to the north and northeast by the city of Bay St. Louis. U.S. Route 90 passes through the northern side of the city, leading east across the Bay of Saint Louis 18 miles to Gulfport and west 55 miles to New Orleans.