Yarmouth is a town in Cumberland County, Maine, United States, twelve miles north of the state's largest city, Portland. When originally settled in 1636, as North Yarmouth, it was part of the Massachusetts Bay Colony, and remained part of its subsequent incarnations for 213 years. In 1849, twenty-nine years after Maine's admittance to the Union as the twenty-third state, it was incorporated as the Town of Yarmouth.

Yarmouth is part of the Portland–South Portland–Biddeford Metropolitan Statistical Area. The town's population was 8,990 in the 2020 census.

The town's proximity to the Atlantic Ocean, and its location on the banks of the Royal River (formerly Yarmouth River), which empties into Casco Bay less than 1 mile (1.6 km) away, means it is a prime location as a harbor. Ships were built in Yarmouth's harbor mainly between 1818 and the 1870s, at which point demand declined dramatically. Meanwhile, the Royal River's four waterfalls within Yarmouth, whose Main Street sits about 90 feet (27 m) above sea level, resulted in the foundation of almost sixty mills between 1674 and 1931.

The annual Yarmouth Clam Festival attracts around 80,000 people (around ten times the town's population) over the course of the three-day weekend.