Sanford is a city in York County, Maine, United States. The population was 21,982 in the 2020 census, making it the seventh largest municipality in the state. Situated on the Mousam River, Sanford includes the village of Springvale. The city features many lakes in wooded areas which attract campers.

York County is the southwesternmost county in the U.S. state of Maine, along the state of New Hampshire's eastern border. It is divided from Strafford County, New Hampshire, by the Salmon Falls River and the connected tidal estuary, the Piscataqua River. York County was permanently established in 1639. Several of Maine's earliest colonial settlements are found in the county, which is the state's oldest and one of the oldest in the United States. As of the 2020 census, its population was 211,972, making it Maine's second-most populous county. Its county seat is Alfred. York County is part of the Portland–South Portland, Maine Metropolitan Statistical Area.