Hinterbrühl is a town in the district of Mödling, in the Austrian state of Lower Austria. It lies within the Vienna Woods region south of Vienna, in the federal province of Lower Austria.
The town is best known for the Seegrotte, a system of caves that includes Europe's largest underground lake. The caverns were originally created by gypsum mining before being flooded, and they now form the centrepiece of the area's main visitor attraction.
During World War II, a satellite camp of the Mauthausen concentration camp was opened inside the caverns. Prisoners held there were used to produce parts for the He 162 Spatz jet fighter.