Scarborough Marsh is a 3,200-acre saltwater marsh owned by the state of Maine and managed by the state's Department of Inland Fisheries and Wildlife as a wildlife management area. It is situated in southern Maine, in the town of Scarborough, in Cumberland County.
The marsh is fed by four rivers and several creeks. Three of the rivers in the Scarborough Marsh feed into and create the Scarborough River, which flows into Saco Bay and the Gulf of Maine.
The main waterways in the marsh are the Libby River, Nonesuch River, Dunstan River, Scarborough River, Jones Creek, Mill Brook, Phillips Brook, Finnerd Brook, and Cascade Brook. There are many other minor creeks that feed the main waterways.
Salt marshes filter pollution from the water and provide food and shelter for numerous species of birds, fish, mammals, and shellfish. Given the wildlife productivity and habitat diversity in this area, Scarborough Marsh is considered by the state of Maine as the most significant of Maine’s coastal Focus Areas. It is the largest salt marsh in the state.
Before the marsh was protected by the state ownership, there was considerable construction on some of the higher lands in and around the marsh, which stretches from Old Orchard Beach, south of Scarborough, nearly to Cape Elizabeth, to the town's north.
The acreage of the Scarborough Marsh Wildlife Management Area continues to grow as a result of organizations such as the Friends of Scarborough Marsh and the Scarborough Land Trust and the town of Scarborough, buying or taking donated ownership of privately held land within or bordering the marshland.
U.S. Route 1 cuts through a section of the marsh in what was formerly referred to as the Dunstan Corner section of the town.
There are two commercial oyster farms and hundreds of commercial and recreational clammers operating in the marsh. Commercial lobstermen dock their boats in one of the rivers. The town provides a limited number of recreational boat tie-ups.