Royal Air Force Menwith Hill or more simply RAF Menwith Hill is a Royal Air Force station near Harrogate, North Yorkshire, England which provides communications and intelligence support services to the United Kingdom and the United States. The site contains an extensive satellite ground station and is a communications intercept missile warning site and has been described as the largest electronic monitoring station in the world.
RAF Menwith Hill is commanded by a Royal Air Force Officer, supported by an RAF element, whilst a large contingent of support services are provided by the United States Air Force, 421st Air Base Group, and US National Security Agency. In 2014, the number of American personnel stationed at Menwith Hill was reduced as part of a streamlining of operations due to improvements in computer and information technology.
The site acts as a ground station for a number of satellites operated by the US National Reconnaissance Office,on behalf of the US National Security Agency, with antennae contained in a large number of highly distinctive white radomes, and is alleged to be an element of the ECHELON system.