The Mad River is a 5.2 mile long (8.4 km) river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in eastern New Hampshire

New Hampshire

New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Cocheco River

Cochecho River

The Cochecho River or Cocheco River is a tributary of the Piscataqua River, 38.3 miles long, in the U.S. state of New Hampshire. It rises in northern Strafford County and runs southeastward, through the town of Farmington and the cities of Rochester and Dover, where it provides hydroelectric power...

, part of the Piscataqua River

Piscataqua River

The Piscataqua River, in the northeastern United States, is a long tidal estuary formed by the confluence of the Salmon Falls and Cocheco rivers...

 watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 leading to the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

.

The river is located entirely in the town of Farmington

Farmington, New Hampshire

Farmington is a town located in Strafford County, New Hampshire, USA. The 2010 census reported that the town had a total population of 6,786. Farmington is home to Blue Job State Forest....

. It rises in Nubble Pond, between Nubble Mountain and Hussey Mountain, and flows northwest, then northeast, reaching the Cocheco near the town center of Farmington. The river drops more than 500 feet over its 5 mile route, frequently falling over scenic ledges.