The Piscataqua River is an tributary of the Presumpscot River in the U.S. state of Maine. Via the Presumpscot River, it is part of the watershed of Casco Bay, an arm of the Atlantic Ocean.
It rises at the outlet of Forest Lake in the southern corner of the town of Gray, flows briefly northeast, then turns southeast and enters the town of Cumberland.
Continuing southwest, it enters Falmouth, turns more south-southeast, and reaches the Presumpscot River just north of the Interstate 495 bridge.