The Oyster River is a 17-mile-long (27 km) river in Strafford County, southeastern New Hampshire, United States. It rises in Barrington, flows southeast to Lee, then east-southeast in a serpentine course past Durham to meet the entrance of Great Bay into Little Bay. The bays are tidal inlets of the Atlantic Ocean, to which they are connected by a tidal estuary, the Piscataqua River. The freshwater portion of the river is 14.1 miles (22.7 km) long, and the tidal river extends 2.9 miles (4.7 km) from Durham to Great Bay.

Lee is a town in Strafford County, New Hampshire, United States. The population was 4,520 at the 2020 census. The town is a rural farm and bedroom community, being close to the University of New Hampshire.