| Middle Branch 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: | Pittsburg, Atkinson & Gilmanton Grant |
| Length: | 9miles |
| Source1 Location: | Pittsburg |
| Source1 Coordinates: | 45.0914°N -71.17°W |
| Source1 Elevation: | 2220feet |
| Mouth: | West Branch Dead Diamond River |
| Mouth Location: | Atkinson & Gilmanton Grant |
| Mouth Coordinates: | 45.0039°N -71.1503°W |
| Mouth Elevation: | 1538feet |
The Middle Branch of the Dead Diamond River is a 9adj=midNaNadj=mid[1] river in northern New Hampshire in the United States. It is a tributary of the West Branch of the Dead Diamond River, located in the Androscoggin River watershed of Maine and New Hampshire.
The Middle Branch flows for most of its length through Pittsburg, the northernmost town in New Hampshire. It flows southeast through a wide valley between 3383feet Magalloway Mountain to the south and 3230feet Diamond Ridge to the north. The river then turns south and flows parallel to the East Branch of the Dead Diamond, entering Atkinson and Gilmanton Grant and joining the West Branch less than one mile upstream from the confluence of the West Branch and the East Branch.