| South Branch Baker 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: | Grafton |
| Subdivision Type4: | Towns |
| Subdivision Name4: | Orange, Groton, Dorchester, Wentworth |
| Length: | 15.6miles |
| Source1 Location: | Orange |
| Source1 Coordinates: | 43.68°N -71.9147°W |
| Source1 Elevation: | 2450feet |
| Mouth: | Baker River |
| Mouth Location: | Wentworth |
| Mouth Coordinates: | 43.8339°N -71.8922°W |
| Mouth Elevation: | 530feet |
| Tributaries Left: | Bucks Brook, Merrill Brook, Rocky Brook |
The South Branch of the Baker River is a 15.6adj=midNaNadj=mid[1] river located in western New Hampshire in the United States. It is a tributary of the Baker River, part of the Pemigewasset River and Merrimack River watersheds.
The river rises in the town of Orange, New Hampshire, on high ground north of Mount Cardigan. It flows north through the southwest corner of the town of Groton and the eastern part of Dorchester, enters Wentworth, and drops rapidly to the Baker River.