The Pisa (Polish pronunciation: [ˈpisa]; German: Pissek) is a river in north-eastern Poland with a length of 80.4 km. It belongs to the Masurian Lake District of the Warmian-Masurian Voivodeship. The Pisa river flows from Lake Roś near the town of Pisz, and is a tributary of the Narew, connecting the Lakeland region with the Vistula.