The Telecommunications Research Establishment (TRE) was the main United Kingdom research and development organization for radio navigation, radar, infra-red detection for heat seeking missiles, and related work for the Royal Air Force (RAF) during World War II and the years that followed. The name was changed to Radar Research Establishment in 1953. This article covers the precursor organizations and the Telecommunications Research Establishment up to the time of the name change. The later work at the site is described in the separate article about RRE.