| South Branch Mad River | |
| Pushpin Map: | New Hampshire#Maine#USA |
| Pushpin Map Size: | 250 px |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | States |
| Subdivision Name2: | New Hampshire, Maine |
| Subdivision Type3: | Counties |
| Subdivision Name3: | Coos, NH, Oxford, ME |
| Subdivision Type4: | Townships |
| Subdivision Name4: | Bean's Purchase, NH, South Oxford, ME |
| Length: | 1.1miles |
| Source1: | West Royce Mountain |
| Source1 Location: | Bean's Purchase, NH |
| Source1 Coordinates: | 44.2908°N -71.0253°W |
| Source1 Elevation: | 2400feet |
| Mouth: | Mad River |
| Mouth Location: | South Oxford, ME |
| Mouth Coordinates: | 44.2858°N -71.0056°W |
| Mouth Elevation: | 807feet |
The South Branch of the Mad River is a 1.1adj=midNaNadj=mid[1] mountain brook on the Maine-New Hampshire border in the United States, within the eastern White Mountains. It is a tributary of the Mad River, a short feeder of the Cold River, part of the Saco River watershed.
The South Branch, beginning in New Hampshire and finishing in Maine, flows east off the slopes of West Royce Mountain. It joins the Mad River less than 0.l mile above that river's end at the Cold River in the floor of Evans Notch.