The Ford Mustang was brought out five months before the normal start of the 1965 production year. The earliest versions are often referred to as 1964½ models, but VIN coded by Ford and titled as 1965 models[8] with production beginning in Dearborn, Michigan on March 9, 1964;[9] the new car was introduced to the public on April 17, 1964[10] at the New York World's Fair.[11]

Executive stylist John Najjar, who was a fan of the World War II P-51 Mustang fighter plane, is credited by Ford to have suggested the name.[12][13] Najjar co-designed the first prototype of the Ford Mustang known as Ford Mustang I in 1961, working jointly with fellow Ford stylist Philip T. Clark.[14] The Mustang I made its formal debut at the United States Grand Prix in Watkins Glen, New York on October 7, 1962, where test driver and contemporary Formula One race driver Dan Gurney lapped the track in a demonstration using the second "race" prototype. His lap times were only slightly off the pace of the F1 race cars.

An alternative view was that Robert J. Eggert, Ford Division market research manager, first suggested the Mustang name. Eggert, a breeder of quarterhorses, received a birthday present from his wife of the book, The Mustangs by J. Frank Dobie in 1960. Later, the book's title gave him the idea of adding the "Mustang" name for Ford's new concept car. The designer preferred Cougar or Torino (and an advertising campaign using the Torino name was actually prepared), while Henry Ford II wanted T-bird II.[15] As the person responsible for Ford's research on potential names, Eggert added "Mustang" to the list to be tested by focus