The Sudbury River is a 32.7-mile-long (52.6 km) tributary of the Concord River in Middlesex County, Massachusetts, in the United States.

Originating in the Cedar Swamp in Westborough, Massachusetts, near the boundary with Hopkinton, the Sudbury River meanders generally northeast, through Fairhaven Bay, and to its confluence with the Assabet River at Egg Rock in Concord, Massachusetts, to form the Concord River.
It has a 162-square-mile (420 km²) drainage area.
A 1775 map identifies the river by this name as passing through the town of Sudbury, itself established 1639.

On April 9, 1999, nearly 17 miles (27 km) of the river were "recognized for their outstanding ecology, history, scenery, recreation values, and place in American literature," by being designated as a part of the National Wild and Scenic Rivers System.
The 14.9-mile (24.0 km) segment of the Sudbury River beginning at the Danforth Street Bridge in the town of Framingham, downstream to the Route 2 bridge in Concord, is designated as a Scenic River, and the 1.7-mile (2.7 km) segment from the Route 2 bridge downstream to its confluence with the Assabet River at Egg Rock is designated as a Recreational River, along with adjoining stretches of the Assabet and Concord rivers.

Mercury contamination was discovered in the 1970s from the Nyanza plant in Ashland.
The EPA subsequently listed the town as a toxic site and led a cleanup effort to repair the damage.
It is still recommended that fish caught downriver not be eaten.
The Sudbury River is a 32.7-mile-long (52.6 km) tributary of the Concord River in Middlesex County, Massachusetts, in the United States.
Originating in the Cedar Swamp in Westborough, Massachusetts, near the boundary with Hopkinton, the Sudbury River meanders generally northeast, through Fairhaven Bay, and to its confluence with the Assabet River at Egg Rock in Concord, Massachusetts, to form the Concord River. It has a 162-square-mile (420 km²) drainage area. A 1775 map identifies the river by this name as passing through the town of Sudbury, itself established 1639.
On April 9, 1999, nearly 17 miles (27 km) of the river were "recognized for their outstanding ecology, history, scenery, recreation values, and place in American literature," by being designated as a part of the National Wild and Scenic Rivers System. The 14.9-mile (24.0 km) segment of the Sudbury River beginning at the Danforth Street Bridge in the town of Framingham, downstream to the Route 2 bridge in Concord, is designated as a Scenic River, and the 1.7-mile (2.7 km) segment from the Route 2 bridge downstream to its confluence with the Assabet River at Egg Rock is designated as a Recreational River, along with adjoining stretches of the Assabet and Concord rivers.
Mercury contamination was discovered in the 1970s from the Nyanza plant in Ashland. The EPA subsequently listed the town as a toxic site and led a cleanup effort to repair the damage. It is still recommended that fish caught downriver not be eaten.
Sudbury River