The Raging Neisse^{[1][lower-alpha 1]} (Polish: Nysa Szalona, German: Wütende Neiße or Jauersche Neiße) is a river in Poland. It has a length of about 51 kilometres (32 mi) and flows into the Kaczawa (Katzbach), which in turn flows into the Oder. Its largest tributary is the Little Neisse.

The Raging Neisse rises at a height of 600 metres (2,000 ft) on the western side of a mountain called the Kokosz on the Waldenburg Heights. It flows down through the lowlands among the foothills of the Sudetes and the heights of Hainau, through the towns of Bolków (Bolkenhain) and Jawor (Jauer). It then merges with the Kaczawa (Katzbach) at a height of 141 metres (463 ft) not far from Jawor near the village of Slup (Schlaup) on the battlefield of the Battle of Katzbach.

During heavy rain and due to its mountainous character, the water level of this small river can rise by up to 2.5 metres or about 8 feet, whence its name, the "Raging" Neisse.

The river became famous as a result of the Battle of Katzbach when fleeing French troops being pursued by Marschall Blücher were driven into the Katzbach and Raging Neisse rivers which were swollen as the result of a thunderstorm.^[2]