The West Branch of the Souhegan River is a 3.1-mile-long (5.0 km)^[1] river in southern New Hampshire in the United States. It is a tributary of the Souhegan River, which flows to the Merrimack River and ultimately to the Gulf of Maine.

West Branch Souhegan River
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Location
Country	United States
State	New Hampshire
County	Hillsborough
Town	New Ipswich
Physical characteristics
Source	Confluence of Pratt Pond Brook and Fox Brook
• location	New Ipswich
• coordinates	42°44′13″N 71°53′14″W / 42.73694°N 71.88722°W / 42.73694; -71.88722
• elevation	1,050 ft (320 m)
Mouth	Souhegan River
• location	New Ipswich
• coordinates	42°43′52″N 71°50′47″W / 42.73111°N 71.84639°W / 42.73111; -71.84639
• elevation	927 ft (283 m)
Length	3.1 mi (5.0 km)
Basin features
Tributaries
• left	Stark Brook

The West Branch is located entirely in the town of New Ipswich, New Hampshire. It begins at the junction of Fox Brook and Pratt Pond Brook, southwest of the town center, and flows east through the settlement known as Smithville, ending at its junction with the South Branch of the Souhegan River north of Gibson Four Corners.