South Portland is a city in Cumberland County, Maine, United States, and is the fourth-most populous city in the state, incorporated in 1898. At the 2020 census, the city population was 26,498. Known for its working waterfront, South Portland is situated on Portland Harbor and overlooks the skyline of Portland and the islands of Casco Bay. Due to South Portland's close proximity to air, marine, rail, and highway transportation options, the city has become a center for retail and industry in the region. The Maine Mall, the largest shopping mall in the state, is located in South 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.