| Little Dead Diamond 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: | Coos |
| Subdivision Type4: | Towns |
| Subdivision Name4: | Clarksville Atkinson & Gilmanton Grant Second College Grant |
| Length: | 7.1miles |
| Source1: | Crystal Mountain |
| Source1 Location: | Clarksville |
| Source1 Coordinates: | 44.9867°N -71.2319°W |
| Source1 Elevation: | 2800feet |
| Mouth: | Dead Diamond River |
| Mouth Location: | Atkinson & Gilmanton Grant |
| Mouth Coordinates: | 44.9747°N -71.1228°W |
| Mouth Elevation: | 1390feet |
| Tributaries Left: | Pesky Brook |
| Tributaries Right: | West Branch, South Branch |
The Little Dead Diamond River is a 7.1adj=midNaNadj=mid[1] river in northern New Hampshire in the United States. It is a tributary of the Dead Diamond River, located in the Androscoggin River watershed of Maine and New Hampshire.
The Little Dead Diamond River rises in the town of Clarksville near the north end of Crystal Mountain, a 7miles ridge with elevations ranging from 2400to above sea level. 3081feet Mount Pisgah lies just to the north of the headwaters. The river flows east into the Atkinson and Gilmanton Academy Grant, where it is joined by its west branch. The river then enters the Dartmouth College Grant and is joined by its south branch. The Little Dead Diamond then turns north, reenters the Atkinson and Gilmanton Grant, and joins the Dead Diamond River near the rapids and old logging camp known as Hell Gate.