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 and 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.