|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, USA|
|- elevation||0 ft (0 m)|
|Length||12 mi (19 km)|
The Piscataqua River, in the northeastern United States, is a 12-mile (19 km) long tidal estuary formed by the confluence of the Salmon Falls and Cocheco rivers. The drainage basin of the river is approximately 1,495 square miles (3,870 km2), encompassing the additional watersheds of the Great Works River and five rivers flowing into Great Bay: the Bellamy, Oyster, Lamprey, Squamscott, and Winnicut.
The river runs southeastward, determining part of the boundary between the states of New Hampshire and Maine, and empties into the Atlantic Ocean east of Portsmouth, New Hampshire. The last six miles before the sea form Portsmouth Harbor, one of the finest harbors in the northeastern United States, despite a tidal current rated as one of the fastest in North America. The city of Portsmouth, New Hampshire and the town of Kittery, Maine 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 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.
See also 
- 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
- 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