|States||New Hampshire, Maine|
|- left||Salmon Falls River|
|- right||Cochecho River, Great Bay|
|Source||Cochecho and Salmon Falls rivers|
|- elevation||0 ft (0 m)|
|- location||Portsmouth Harbor, New Hampshire/Maine border, United States|
|- elevation||0 ft (0 m)|
|Length||12 mi (19 km)|
The Piscataqua River /, /) is a 12-mile-long (19 km) tidal river forming the boundary of the U.S. states of New Hampshire and Maine from its origin at the confluence of the Salmon Falls River and Cocheco River. The drainage basin of the river is approximately 1,495 square miles (3,870 km2), including the subwatersheds of the Great Works River and the five rivers flowing into Great Bay: the Bellamy, Oyster, Lamprey, Squamscott, and Winnicut.
The river runs southeastward, with New Hampshire to the south and west and Maine to the north and east, and empties into the Gulf of Maine east of Portsmouth, New Hampshire. The last 6 miles (10 km) before the sea form Portsmouth Harbor, one of the finest harbors in the northeastern United States, despite a tidal current of around 4 knots (7.4 km/h; 4.6 mph). The cities/towns of Portsmouth, New Castle, Newington, Kittery and Eliot have developed around the harbor.
Named by the area's original Abenaki inhabitants, Piscataqua is believed to be a combination of peske (branch) with tegwe (a river with a strong current, possibly tidal). The first known European to explore the river was Martin Pring in 1603. Captain John Smith placed a spelling similar to "Piscataqua" for the region on his map of 1614. The river was the site of the first sawmill in the colonies in 1623, the same year the contemporary spelling "Piscataqua" was first recorded.
The Portsmouth Naval Shipyard is located on Seavey's Island in Kittery, Maine, near the Piscataqua's mouth. The dispute between New Hampshire and Maine over ownership of Seavey's Island was settled by the U.S. Supreme Court in 2001, locating the state border at the center of the river's navigable channel.
- Badger's Island
- Great Bay (New Hampshire)
- List of rivers of Maine
- List of rivers of New Hampshire
- Memorial Bridge (Portsmouth, New Hampshire)
- Piscataqua River Bridge
- Prescott Park (New Hampshire)
- Sarah Mildred Long Bridge
- MaineRivers.org Piscataqua River
- History as Border of New Hampshire
- Seacoast Forts of Portsmouth Harbor from American Forts Network
- Port of New Hampshire
- NOAA "Tides & Currents fact sheet" - "Nobles Island, north of"
- DeLorme Mapping Company The Maine Atlas and Gazetteer (13th edition) (1988) ISBN 0-89933-035-5 map 1
- Derivation of Piscataqua.
- Max Hastings, Inferno, New York 2011, p. 630.
- "Supreme Court Collection". Cornell Law School. Retrieved 2007-05-22.
- Ralph May, Piscataqua, The Correctness of Use and the Meaning of the Word (1966), Randall Press, Portsmouth, New Hampshire
- New Hampshire v. Maine (2001) U.S. Supreme Court Case regarding border dispute