The Lockheed A-12 was a reconnaissance aircraft built for the United States Central Intelligence Agency (CIA) by Lockheed's Skunk Works, based on the designs of Clarence "Kelly" Johnson. The aircraft was designated A-12, the 12th in a series of internal design efforts for "Archangel", the aircraft's internal code name. It competed in the CIA's "Oxcart" program against the Convair Kingfish proposal in 1959, and won for a variety of reasons.

CIA's representatives initially favored Convair's design for its smaller radar cross-section, but the A-12's specifications were slightly better and its projected cost was much less. The companies' respective track records proved decisive. Convair's work on the B-58 had been plagued with delays and cost overruns, whereas Lockheed had produced the U-2 on time and under budget. In addition, it had experience running a “black” project.

The A-12 was produced from 1962 to 1964, and operated from 1963 to 1968. It was the precursor to the twin-seat U.S. Air Force YF-12 prototype interceptor, M-21 drone launcher, and the SR-71 Blackbird, a slightly longer variation able to carry a heavier fuel and camera load. The A-12's final mission was flown in May 1968, and the program and aircraft retired in June. The program was officially revealed in the mid-1990s.

A CIA officer later wrote, "OXCART was selected from a random list of codenames to designate this R&D and all later work on the A-12. The aircraft itself came to be called that as well." The crews named the A-12 the Cygnus, suggested by pilot Jack Weeks to follow the Lockheed practice of naming aircraft after celestial bodies.