- The European Southern Observatory (ESO, also more formally the European Organisation for Astronomical Research in the Southern Hemisphere) is an intergovernmental research organisation for astronomy, composed and supported by eleven countries from the European Union plus Switzerland.
- Created in 1962, it is famous for building and operating some of the largest and most technologically advanced telescopes in the world in the Atacama Desert, such as the New Technology Telescope (NTT), which was one of the telescopes which pioneered active optics technology, and more recently the VLT (Very Large Telescope), consisting of four 8-meter class telescopes.
- Its numerous observing facilities have made many astronomical discoveries, and produced several astronomical catalogues. Among the more recent are the farthest galaxy ever seen by humans, the Abell 1835 IR1916 galaxy, though this claim seems to be debunked by a series of new articles. In 2005, it obtained the first picture of an exosolar planet, 2M1207b, orbiting a brown dwarf 260 light-years away.