Mitchel Air Force Base, also known as Mitchel Field, was a United States Air Force base located on the Hempstead Plains of Long Island, New York, United States. Established in 1918 as Hazelhurst Aviation Field #2, the facility was renamed later that year as Mitchel Field in honor of former New York City Mayor John Purroy Mitchel, who was killed while training for the Air Service in Louisiana.

Decommissioned in 1961, Mitchel Field became a multi-use complex that is home to the Cradle of Aviation Museum, Nassau Coliseum, Mitchel Athletic Complex, Nassau Community College, Hofstra University, and Lockheed. In 2018, the surviving buildings and facilities were recognized as a historic district and listed on the National Register of Historic Places.

During the American Revolutionary War it was known as the Hempstead Plains and used as an Army enlistment center. In the War of 1812 and in the Mexican War, it was a training center for Infantry units. During the American Civil War, it was the location of Camp Winfield Scott. In 1898, in the Spanish–American War, Mitchel's site was known as Camp Black.

In 1917, Hazelhurst Field #2 was established south of and adjacent to Hazelhurst Field to serve as an additional training and storage base, part of the massive Air Service Aviation Concentration Center. Curtiss JN-4 Jennies became a common sight over Long Island in 1917 and 1918. Hundreds of aviators were trained for war at these training fields, two of the largest in the United States. Numerous new wooden buildings and tents were erected on Roosevelt Field and Field #2 in 1918 in order to meet this rapid expansion.

Mitchel Field continued to grow after World War I and between 1929 and 1932. An extensive building program was undertaken after the war to turn the temporary wartime facilities into a permanent Army post, with new barracks, warehouses, hangar space, and administrative buildings. Much of this construction still exists today, being used for non-military purposes.

In the 1920s and 1930s, various observation, fighter, and bomber units were stationed at the airfield. It became a major aerodrome for both the Air Corps as well as various civilian activity. The 1920s was considered the golden age of air racing and on 27 November 1920, the Pulitzer Trophy Race was held at Mitchel Field. The race consisted of four laps of a 29 miles (47 km) course. 38 pilots entered and took off individually. The winner was Capt. Corliss Moseley, flying a Verville-Packard VCP-R racer, a cleaned-up version of the Army's VCP-1 pursuit plane, at 156.54 miles per hour (251.93 km/h).

In October 1923, Mitchel Field was the scene of the first airplane jumping contest in the nation. During the same year, two world's airplane speed records were established there. In 1924, the airmail service had its inception in experimental flights begun at the airfield. In September 1929, Lt. Gen. James H. Doolittle, then a Lieutenant, made the world's first blind flight.

In 1938, Mitchel was the starting point for the first nonstop transcontinental bomber flight, made by Army B-18 Bolo bombers. Mitchel Field also served as a base from which the first demonstration of long-range aerial reconnaissance was made. In May 1939, three B-17s, with Lt. Curtis LeMay navigating, flew 620 miles (1,000 km) out to sea and intercepted the Italian ocean liner SS Rex. This was a striking example of the range, mobility, and accuracy of modern aviation at the time. On September 21 of that year the base was struck by the "Long Island Express" hurricane. Flooding produced water that was over knee-deep, numerous trees were toppled and the glass was smashed atop the traffic control tower.