| East Branch Union River | |
| Mouth Location: | Union River |
| Mouth Coordinates: | 44.7315°N -68.381°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Mouth Elevation: | 32feet |
| Tributaries Left: | Bog River |
| Tributaries Right: | Middle Branch Union River |
The East Branch Union River is a 21.6adj=midNaNadj=mid[1] river in Hancock County, Maine. From the outflow of Rocky Pond (44.7924°N -68.1427°W) in Maine Township 22 M D, the river runs [1] southwest to Spectacle Pond in Osborn. From the pond's outlet, the river runs [1] northwest, southwest, west and southwest to Graham Lake, where it joins the West Branch to form the Union River. The lower section of the East Branch forms the border between Mariaville and Waltham.