The Douglas X-3 Stiletto was an experimental aircraft developed by the Douglas Aircraft Company in the 1950s for the United States Air Force. The X-3 was designed to test advanced aerodynamic concepts and technologies, including supersonic flight and swept-wing configurations.

The X-3 was a sleek, jet-powered aircraft with a distinctive, needle-like fuselage and thin, straight wings. It was powered by two Westinghouse J34 turbojet engines, which gave it a top speed of Mach 1.2. The aircraft was also equipped with a variety of experimental sensors and instruments, including a nose-mounted camera for recording flight data.

Despite its advanced design and technology, the X-3 suffered from a number of technical problems during its development and testing. Its straight wings proved to be less efficient at high speeds than the swept-wing configurations that would become standard on supersonic aircraft. The aircraft also had a relatively short service life, flying only a few test flights before being retired from active service.

Despite its limited success, the X-3 Stiletto contributed valuable data to the development of supersonic aircraft and advanced aerodynamic concepts.