The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets and personnel were transferred to the newly created National Aeronautics and Space Administration (NASA). NACA is an initialism, i.e., pronounced as individual letters, rather than as a whole word (as was NASA during the early years after being established).

Among other advancements, NACA research and development produced the NACA duct, a type of air intake used in modern automotive applications, the NACA cowling, and several series of NACA airfoils, which are still used in aircraft manufacturing.

During World War II, NACA was described as "The Force Behind Our Air Supremacy" due to its key role in producing working superchargers for high altitude bombers, and for producing the laminar wing profiles for the North American P-51 Mustang. NACA also helped in developing the area rule that is used on all modern supersonic aircraft, and conducted the key compressibility research that enabled the Bell X-1 to break the sound barrier.