| Little Southwest Branch Saint John River | |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Maine |
| Subdivision Type3: | County |
| Subdivision Name3: | Somerset County, Maine |
| Source1 Location: | Mountain brook, Somerset County, Maine, Maine |
| Source1 Coordinates: | 46.1261°N -70.1936°W |
| Source1 Elevation: | 495m (1,624feet) |
| Mouth Location: | Southwest Branch Saint John River |
| Mouth Coordinates: | 46.1261°N -70.1936°W |
| Mouth Elevation: | 363m (1,191feet) |
| Length: | 46.5km (28.9miles) |
| Tributaries Left: | Black brook |
The Little Southwest Branch Saint John River is a tributary of Southwest Branch Saint John River, flowing on [1] in Somerset County, in North Maine Woods, in Maine, in United States.
From its source (46.126°N -70.1941°W) in Maine Township 6, Range 19, WELS, it flows northward in a deep valley in forest area, a few miles east of the Canada–United States border to its mouth on South bank of the Southwest Branch Saint John River in T 9, R 18.
The source of the "Little Southwest Branch Saint John River" is located in the Big SIX region, in Township 6, Range 19 Wels, in the Somerset County, Maine, in northern Maine. The upper part of the "Little Southwest Branch Saint John River" proves to be the continuity towards the North of the Valley "Middle Branch Norris Brook", a tributary of Norris Brook which in turn is a tributary of the Penobscot River.
The source of the "Little Saint John West River" is located at:
From its source, the "Little Southwest Branch Saint John River" runs on, in these segments:
"Little Southwest Branch Saint John River" flows on the south bank of the Southwest Branch Saint John River, which forms the border between Canada (Quebec) and United States (Maine) in this area.
The place name "Little Southwest Branch Saint John River" derives from the name of the main river designated Southwest Branch Saint John River.