The Pasłęka (Ger. Passarge) is a long river in Poland that debouches into the Baltic Sea on the Vistula Lagoon near Braniewo. It flows through the lake areas of Olsztyn and Mrągowo, and through Gdańsk Coastal Area.
The reported length of the river varies, depending on sources, from169 to 211 kilometres (105 to 131 mi).
The river springs nearby Olsztynek, between Stawiguda and Gryźliny, at 156.6 meters (514 ft) AMSL; though some sources place it in the Pasłęk reservoir, which lies at 153 m (502 ft) AMSL.
The river flows through the town of Braniewo (until 1945 the German town of Braunsberg).
The drainage area of Pasłęka spreads over 2,330 square kilometres (900 sq mi).
Pasłęka's average mouth discharge equals 15.7 m3/s (550 cu ft/s).
The whole length of the river is covered by River Pasłęka Beaver Refugium nature reserve.
Pasłęka is one of Warmia's two main rivers, accompanied by Łyna.
Pasłęka divides two historical lands: Warmia and Upper Prussia, consequently for centuries bordering the state of Prussia and Polish Warmia.