The Galileo satellite navigation system is a planned European satellite navigation system, similar to NAVSTAR-GPS (the US military's global positioning system), but run on a purely civilian basis. It is being developed by ESA (the European Space Agency) in collaboration with the European Union – the first such joint project – and is expected to be fully operational by 2010. Its goal is to provide the world in general and Europeans in particular with an accurate, secure, and certified satellite positioning system with applications in road, rail, air, and maritime traffic control, synchronization of data transmission between banks, and so forth. Although Galileo will be incommercial competition with NAVSTAR-GPS (and so, not surprisingly, has been opposed by the American government), it will also complement GPS and provide redundancy.

The Galileo system will consist of 30 satellites (27 in operation and 3 in reserve), deployed in three circular medium Earth orbits at an altitude of 23,616 km and an inclination of 56° to the equator. Two control centers will be set up in Europe to monitor the operation of the satellites and manage the navigation system. A precursor of the system is EGNOS (European Global Navigation Overlay Service), which refines current GPS data and foreshadows the servives Galileo will provide.