Southwest Harbor is a census-designated place (CDP) in the town of Southwest Harbor in Hancock County, Maine, United States.

Both inlets are located at the southern end of Somes Sound, an arm of the Gulf of Maine.

[3] Maine State Route 102 passes through Southwest Harbor, leading southwest 2.5 miles (4.0 km) to Tremont and north 6 miles (10 km) to Somesville at the north end of Somes Sound.

Route 102A splits east from Route 102 at the southern end of the Southwest Harbor CDP, and makes a loop through Seawall and Bass Harbor, reaching Tremont in 7 miles (11 km).

According to the United States Census Bureau, the Southwest Harbor CDP has an area of 1.4 square miles (3.5 km2), all land.