The Fore River is a short horn-shaped estuary, approximately 4 mi (6.4 km) long, separating Portland and South Portland in Maine in the United States. Many of the port facilities of the Portland harbor are along the estuary, which is formed just southwest of Portland by the confluence of several creeks. It enters Casco Bay on the southeast edge of Portland. Like other coastal areas along the Gulf of Maine, it experiences moderately high tides and thus the water level in the estuary and the harbor varies greatly throughout the day, leaving mud flats at low tide. It is spanned by several bridges, including one that carries I-295.