The Schwarza is a river in Lower Austria. It is a headstream of the River Leitha.It rises on the saddle of Rohrer Sattel, flows through the Höllental gorge and the Schwarza valley. Near Haderswörth in the parish of Lanzenkirchen the Schwarza combines with the Pitten and is then called the Leitha. It is 78 kilometres (48 mi) long. The Schwarza is part of the Natura 2000 region known as "North Eastern Border Alps: Hohe Wand – Schneeberg – Rax".