The Lockheed YF-12 was an American Mach 3+ capable, high-altitude interceptor prototype, developed and manufactured by American aerospace company Lockheed Corporation.

The interceptor was developed during the late 1950s and early 1960s as a potential replacement for the F-106 Delta Dart interceptor for the United States Air Force (USAF). The YF-12 was a twin-seat version of the then-secret single-seat Lockheed A-12 reconnaissance aircraft operated by the Central Intelligence Agency (CIA); unlike the A-12, it was furnished with the Hughes AN/ASG-18fire-control radar and could be armed with AIM-47 Falcon (GAR-9) air-to-air missiles. Its maiden flight was on 7 August 1963. Its existence was publicly revealed by President Lyndon B. Johnson on 24 February 1964; this move was to provide plausible deniability for the CIA-operated A-12 fleet, which closely resembled the prototype YF-12.