Chalgrove Airfield (IATA: N/A, ICAO: EGLJ) is a former World War II airfield in Oxfordshire, England. The airfield is located approximately 3 miles (4.8 km) north-northeast of Benson; about 42 miles (68 km) north-northwest of London

Opened in 1943, it was used by both the Royal Air Force and United States Army Air Force. During the war it was used primarily as a combat Reconnaissance airfield. After the war it was closed in late 1946.

Today, the airfield is primarily used by the Martin-Baker company for testing ejector seats.

Chalgrove Airfield was one 16 airfields west of London and south of Oxford built to bomber standards for use by American transport or reconnaissance units, and was constructed in 1943 primarily by Alfred McAlpine.

The airfield conformed to the Class A airfield standard, the main feature of which was a set of three converging runways each containing a concrete runway for takeoffs and landings, optimally placed at 60 degree angles to each other in a triangular pattern. It had a 6,004 ft main runway (13/31) and secondary runways of 4,347 ft (06/24) and 4,186 ft (18/36) respectively. 50 hardstands were also constructed of standard loop type along with two T-2 hangars connecting to an enclosing perimeter track, of a width of 50 feet.

The ground support station was constructed largely of Nissen huts of various sizes. The support station was where the group and ground station commanders and squadron headquarters and orderly rooms were located. Also on the ground station were where the mess facilities; chapel; hospital; mission briefing and debriefing; armory and bombsite storage; life support; parachute rigging; supply warehouses; station and airfield security; motor pool and the other ground support functions necessary to support the air operations of the group. These facilities were all connected by a network of single path support roads.

The technical site, connected to the ground station and airfield consisted of at least two T-2 type hangars and various organizational, component and field maintenance shops along with the crew chiefs and other personnel necessary to keep the aircraft airworthy and to quickly repair light and moderate battle damage. Aircraft severely damaged in combat were sent to repair depots for major structural repair. The Ammunition dump was located on the northwest side of the airfield, outside of the perimeter track surrounded by large dirt mounds and concrete storage pens for storing the aerial bombs and the other munitions required by the combat aircraft.

Various domestic accommodation sites were constructed dispersed away from the airfield, but within a mile or so of the technical support site, also using clusters of Maycrete or Nissen huts. The Huts were either connected, set up end-to-end or built singly and made of prefabricated corrugated iron with a door and two small windows at the front and back. They provided accommodation for 2,557 personnel, including communal and a sick quarters

The RAF opening party arrived on 21 November 1943 and the airfield was first opened in January 1944 when the first US personnel arrived.

Chalgrove was allocated to the USAAF by the Ministry of Defence on 1 November 1942. The station's proximity to the RAF photographic reconnaissance base at RAF Benson and the Eighth Air Force's similar installation at RAF Mount Farm earmarked the base for the photoreconnaissance mission of the Ninth Air Force.