The Royal Observatory, Greenwich (formerly the Royal Greenwich Observatory or RGO), in London played a major role in the history of astronomy and navigation, and is best known as the location of the prime meridian. It is situated on a hill in Greenwich Park, overlooking the River Thames.

The observatory was commissioned in 1675 by King Charles II, and remains at Greenwich as a testament of the pioneering work in navigation undertaken by Earnshaw and his peers in the fields of timekeeping, and cartography.