Saco is a city in York County, Maine, United States. The population was 20,381 at the 2020 census. It is home to Ferry Beach State Park, Funtown Splashtown USA, Thornton Academy, as well as General Dynamics Armament Systems, a subsidiary of the defense contractor General Dynamics. Saco sees much tourism during summer months due to its amusement parks, Camp Ellis Beach and Pier, Ferry Beach State Park, and proximity to Old Orchard Beach.

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.