Observatory, in astronomy, a building or group of buildings from which the heavens are studied. Observatories range in size from a single small building in an amateur astronomer's backyard to huge complexes where many professional astronomers work and live. Professional observatories are operated by universities, governments, and private research institutions. An orbiting observatory is an assembly of astronomical instruments installed in an artificial satellite.

There are two basic types of ground observatoriesoptical and radio.