| Mad River | |
| Pushpin Map: | New Hampshire#USA |
| Pushpin Map Size: | 250 px |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | New Hampshire |
| Subdivision Type3: | County |
| Subdivision Name3: | Strafford |
| Subdivision Type4: | Town |
| Subdivision Name4: | Farmington |
| Length: | 5.2miles |
| Source1: | Nubble Pond |
| Source1 Location: | Farmington |
| Source1 Coordinates: | 43.3511°N -71.1003°W |
| Source1 Elevation: | 715feet |
| Mouth: | Cochecho River |
| Mouth Location: | Farmington village |
| Mouth Coordinates: | 43.3864°N -71.0672°W |
| Mouth Elevation: | 270feet |
The Mad River is a 5.2adj=midNaNadj=mid[1] river in eastern New Hampshire in the United States. It is a tributary of the Cochecho River, part of the Piscataqua River watershed leading to the Atlantic Ocean.
The river is located entirely in the town of Farmington. It rises in Nubble Pond, between Nubble Mountain and Hussey Mountain, and flows northwest, then northeast, reaching the Cochecho near the town center of Farmington. The river drops more than 500feet over its 5miles route, in places falling over scenic ledges.