| South Branch Sugar 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: | Sullivan |
| Subdivision Type4: | Towns |
| Subdivision Name4: | Goshen, Newport |
| Length: | 6.6miles |
| Source1: | Confluence of Blood Brook and Gunnison Brook |
| Source1 Location: | Goshen |
| Source1 Coordinates: | 43.3011°N -72.1503°W |
| Source1 Elevation: | 291m (955feet) |
| Mouth: | Sugar River |
| Mouth Location: | Newport |
| Mouth Coordinates: | 43.3619°N -72.1742°W |
| Mouth Elevation: | 238m (781feet) |
| Tributaries Left: | Coon Brook, Spring Brook |
The South Branch of the Sugar River is a 6.6adj=midNaNadj=mid[1] river located in western New Hampshire in the United States. It is a tributary of the Sugar River, which flows to the Connecticut River, which flows to Long Island Sound.
The South Branch begins at the confluence of Gunnison Brook and Blood Brook at the center of the town of Goshen, New Hampshire. The river flows north, reaching the Sugar River near the center of the town of Newport. New Hampshire Route 10 follows the South Branch for its entire length.