Royal Air Force Leeming or more simply RAF Leeming is a Royal Air Force station located near Leeming, North Yorkshire, England. It was opened in 1940 and was jointly used by the RAF and the Royal Canadian Air Force (RCAF). Between 1950 and 1991, it operated mostly as a training base with Quick Reaction Force (QRF) Panavia Tornado F3 fighters based there in the latter stages of the Cold War and into the early 21st century. Since 2006, it has become the home of the deployable RAF communications cadre (No. 90 Signals Unit RAF) and the home of No. 135 Expeditionary Air Wing.
 The area at the extreme western edge of the base was used in the 1930s by local flying enthusiasts. It took the name of Londonderry Aerodrome as it was closest to the hamlet of Londonderry in North Yorkshire. In the late 1930s, the Royal Air Force bought up the aerodrome and most of the surrounding land to convert it into an RAF airfield, which became known as Royal Air Force Leeming. Part of the buildup of the base included building a decoy airfield at Burneston, some 4 miles (6.4 km) to the south.
 The station opened in June 1940 as a bomber station during the Second World War. In 1943 the station was assigned to No. 6 Group Royal Canadian Air Force (RCAF) with a sub-station at RAF Skipton-on-Swale. The main aircraft operated were Handley Page Halifax bombers.
 A detachment of No. 219 Squadron RAF used the airfield between 4 October 1939 and 12 October 1940 when the main section of the squadron was at RAF Catterick flying the Bristol Blenheim IF.
 Following the war, the station became a night-fighter base, equipped initially with de Havilland Mosquito and then Gloster Meteor and Gloster Javelin aircraft before becoming a Flying Training Command airfield in 1961. The station was then home to No. 3 Flying Training School, equipped with the BAC Jet Provost aircraft.
 There were also several other units using the airfield during the same period, these were:
 In January 1987, the airfield closed for one year to allow installation of Hardened Aircraft Shelters (HAS). RAF Leeming became the home base for three Tornado squadrons over the next twenty years.
 Leeming functioned as a training base until 1988 when it became a front line base in the air defence role equipped with Panavia Tornado F.3s. Its new runway was opened by Station Commander Wing Commander Kit Smith on 11 January 1988. Initially it hosted Nos 11(F), 23, and 25(F) Squadrons, all flying the F3. 23 Squadron was disbanded on 1 March 1994 and its air and ground crews dispersed across the station's remaining two squadrons. This left two Tornado squadrons, which were half of the air defence fighter squadrons of the RAF. 11 Squadron was disbanded in October 2005. The last Tornado squadron at Leeming, No 25(F) Squadron, disbanded on 4 April 2008. No. 100 Squadron RAF with Hawk T.1As arrived on 21 September 1995 from RAF Finningley.
 No. 135 Expeditionary Air Wing was formed at Leeming on 1 April 2006 to create a deployable air force structure. Since that time it has deployed several times for Baltic Air Policing.
 The station's air traffic control unit was named the best in the Royal Air Force in February 2012, winning the Raytheon Falconer Trophy.
 RAF Leeming had been host to a BAE Systems reverse assembly line process (Reduce to Produce (RTP)) programme in which redundant Tornado aircraft were brought into one of the hangars at RAF Leeming and stripped of all usable components. The process started with the F3 variant of the aircraft as it was the first to be withdrawn completely from service, and moved onto the GR4 variant later. In October 2017, it was announced that the full retirement of the Tornado aircraft from RAF service in 2019 meant that this process would end with the loss of 245 British Aerospace jobs between RAF Leeming and RAF Marham.
 607 (County of Durham) Squadron reformed at RAF Leeming on 5 January 2015. The Squadron formerly flew fighter aircraft and was disbanded in 1957. The squadron is a General Service Support (GSS) unit with many diverse roles such as chef, driver, intelligence analyst and suppliers.
 In March 2019, the Ministry of Defence indicated that RAF Leeming, alongside RAF Waddington and RAF Wittering, was being considered as the future home of the RAF Aerobatic Team the Red Arrows. In May 2020 however it was confirmed that the team would move to Waddington.
 On 22 April 2020, the government announced that alpha testing of a prototype of the government's COVID-19 app was in progress at RAF Leeming.
 On 1 December 2020, it was announced that the Yorkshire Universities Air Squadron had relocated to RAF Leeming from RAF Linton-on-Ouse as part of the latter's closure by the end of 2021.
 The first of nine Hawk 167 aircraft to be operated by a newly established Joint Qatar Emiri Air Force-RAF Hawk Training Squadron arrived at Leeming in early September 2021. The squadron will train pilots from both air forces and be home to the Qatar Emiri Air Force's entire fleet of Hawks. The RAF's No. 100 Squadron, operating the Hawk T1 in the aggressor role disbanded on 31 March 2022.
 The deployable elements of the station structure form the core of an Expeditionary Air Wing, No. 135 Expeditionary Air Wing. For Exercise 'Griffin Strike 2016' in April 2016, No. 135 EAW became the combined French-British No. 135 Combined Expeditionary Air Wing.
 Flying and notable non-flying units based at RAF Leeming.
 No. 1 Group (Air Combat) RAF
 No. 2 Group (Air Combat Support) RAF
 No. 22 Group (Training) RAF
  
 Leeming's gate guardian is now a Tornado F3, commemorating its history as an air defence base, and the fact that many Tornados were scrapped/Reduced To Produce here. The previous gate guardian XA634 is the world's only surviving Gloster Javelin FAW4, which spent most of its life as a testbed at the Gloster Aircraft Company and was offered for sale by tender in September 2014 by the Ministry of Defence. In December 2014 it was announced that Gloucestershire Jet Age Museum had won the tender and purchased the aircraft.