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 centimetres (27 in) and a focal length of 10.5 metres (34 ft) built by the Grubb Telescope Company. At that time, it was the world's largest refracting telescope.