Yarmouth is a town in Cumberland County, Maine, United States, located approximately ten to fifteen miles north of Portland, the state's largest city. Its population was 8,360 at the 2000 census.

Yarmouth is part of the Portland–South Portland-Biddeford Metropolitan Statistical Area.

According to the United States Census Bureau, the town has a total area of 22.8 square miles (59.0 km²), of which, 13.3 square miles (34.6 km²) of it is land and 9.4 square miles (24.4 km²) of it (41.44%) is water.

Yarmouth is nearly square in form, and is bisected by the Royal River. Cousins River separates it from Freeport to the north-east. Freeport and Pownal bound it to the east, North Yarmouth to the north, Cumberland to the west and Casco Bay to the south. Also included as part of the town are Cousins Island, Lane's Island, Great and Little Mosier, Littlejohn and Crab islands.