Universitäts-Sternwarte Wien (Vienna Observatory) is an astronomical observatory in Vienna, Austria. It is part of the University of Vienna. The first observatory was built in 1753/1754 on the roof of one of the university buildings.
A new observatory was built between 1874 and 1879, and was finally inaugurated by Emperor Franz Joseph I of Austria in 1883. The main dome houses a refractor with a diameter of 68 centimeters and a focal length of 10.5 meters. At that time, this was the world's largest telescope.