Saint-Simon – Clastres Air Base (French: Base aérienne de Saint-Simon - Clastres) (ICAO: LFYT) is an abandoned military airfield, which is located approximately 3 km (2 NM) northwest of Clastres and east of Saint-Simon, both communes in the Aisne department of the Picardy (Picardie) region in France. It is approximately 116 km (63 NM) north-northeast of Paris.

Its history begins before World War II when it was originally a grass civil airdrome. During the German occupation of France (1940–1944), the Luftwaffe developed the airdrome into a major military airfield. Attacked frequently by Allied Air Forces, the Luftwaffe base was seized by Allied Ground Forces in September 1944 and was used as a Fighter and bomber base by the United States Army Air Force until the end of the war. It was redeveloped in the 1950s as a NATO Dispersed Operating Base and was closed in 1967.

Today, it is mostly agricultural fields, and also a power-generating wind farm, with several electric generating windmills.