The Ministry of Defence is the British government department responsible for defence policy and the headquarters of the armed forces, based in the Main Building in Whitehall, London. Its modern form dates from April 1, 1964, when the Admiralty, War Office and Air Ministry merged into a single department under the Secretary of State for Defence. From the early 1950s until 2009 the ministry and its Air Ministry predecessor were also the official recipients of British UFO reports, which makes them the main source of government records on the subject in the United Kingdom.

That role began in October 1950, when the ministry's chief scientific adviser, Sir Henry Tizard, set up the Flying Saucer Working Party; its June 1951 report attributed the sightings it studied to natural or conventional causes and recommended no further investigation. Reports kept arriving, and a small Air Staff secretariat desk assessed them for defence significance. Nick Pope, who worked on that desk from 1991 to 1994, became Britain's best-known UFO commentator after leaving it; he passed away in April 2026. The desk's files include the memo on the 1980 Rendlesham Forest incident and papers on the 1990 Calvine photograph. Between 1997 and 2000 the Defence Intelligence Staff's DI55 section reviewed about 10,000 reports in a study known as Project Condign. Released in 2006 after a Freedom of Information request, it attributed most sightings to misidentified aircraft, balloons and other ordinary objects, attributed the unexplained remainder to a proposed plasma phenomenon and found no evidence that the objects were hostile or under any type of control.

The ministry stopped investigating reports in 2009, explaining later that in more than 50 years no sighting reported to it had indicated any military threat to the United Kingdom. It passed its UFO records to The National Archives, which with journalist David Clarke as consultant released about 210 files, some 60,000 pages, in ten tranches between 2008 and 2013. Its published logs of sightings from 1997 to 2009 are still used by researchers mapping British reports.

The ministry's position drew new scrutiny in 2025 and 2026. Answering Labour MP Clive Lewis in September 2025, armed forces minister Luke Pollard said the department had conducted or commissioned no UAP studies, that all relevant material up to 2009 was public at The National Archives and that it had "not participated in any international groupings specifically focused on" UAP since May 2023. In August 2026 Lewis told the Sol Foundation he had been "definitely misled," after Liberation Times reported that the ministry had confirmed two of its defence intelligence officials attended the first Five Eyes UAP caucus meeting on May 24, 2023. According to Liberation Times, the ministry declined to say whether British involvement continued.

Today the ministry treats unidentified aerial reports as routine air-defence and air-safety matters rather than a subject for dedicated study, a contrast with the standing UAP office and congressionally mandated releases in the United States. Its transferred archive of nearly six decades of reports is one of the fullest public records of how a national military establishment handled UFO sightings.