Casco is a town in Cumberland County, Maine, United States. Casco is included in the Lewiston-Auburn, Maine metropolitan New England city and town area. The population was 3,646 at the 2020 census. Casco includes the villages of Casco, South Casco and Cook Mills. The town borders the east shore of Sebago Lake, and is home to part of Sebago Lake State Park. Casco is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area. Casco is just under 30 miles (48 km) from downtown Portland.

Cumberland County is a county in the U.S. state of Maine. As of the 2020 census, the population was 303,069, making it the most populous county in Maine. Its county seat is Portland. Cumberland County was founded in 1760 from a portion of York County, Province of Massachusetts Bay, and named for William, Duke of Cumberland, a son of King George II. Cumberland County has the deepest and second-largest body of water in the state, Sebago Lake, which supplies tap water to most of the county. The county is the state's economic and industrial center, having the resources of the Port of Portland, the Maine Mall, and having corporate headquarters of major companies such as Fairchild Semiconductor, IDEXX Laboratories, Unum, and TD Bank. Cumberland County is part of the Portland–South Portland, ME Metropolitan Statistical Area.