| South Branch Piscataquog 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: | Hillsborough |
| Subdivision Type4: | Towns |
| Subdivision Name4: | Francestown, Lyndeborough, New Boston, Goffstown |
| Length: | 20.5miles |
| Source1: | Pleasant Pond |
| Source1 Location: | Francestown |
| Source1 Coordinates: | 43.0242°N -71.8175°W |
| Source1 Elevation: | 817feet |
| Mouth: | Piscataquog River |
| Mouth Location: | Goffstown |
| Mouth Coordinates: | 43.0231°N -71.6231°W |
| Mouth Elevation: | 290feet |
| Tributaries Left: | Middle Branch Piscataquog |
| Tributaries Right: | Collins Brook, Rand Brook, Cold Brook, Lords Brook, Meadow Brook |
The South Branch of the Piscataquog River is a 20.5adj=midNaNadj=mid[1] river located in southern New Hampshire in the United States. It is a tributary of the Piscataquog River, part of the Merrimack River watershed.
The South Branch of the Piscataquog begins at the outlet of Pleasant Pond in Francestown, New Hampshire. The river travels south-southeast until entering New Boston, where it turns northeast to flow to the Piscataquog River just over the town line in Goffstown. For most of its route, the South Branch passes through rolling, hilly country, occasionally dropping over small waterfalls. New Hampshire Route 13 follows the river closely from New Boston to Goffstown.