The internal project code name for the first Ford Mustang was T-5. Ford used the designation during the car’s development before the Mustang name became public.
The project began in 1962 under Ford vice president Lee Iacocca and the Fairlane Group. The team wanted an affordable, stylish four-seat car that would appeal to younger buyers. To control costs and speed development, engineers adapted components from existing Ford models, especially the compact Falcon.
T-5 did not disappear entirely when the Mustang went on sale. Ford also used the name for early prototypes and for Mustangs exported to Germany. A German company, Krupp, controlled the rights to the Mustang name in that market, so Ford-badged export cars were sold as T-5s instead. Those cars were mechanically Mustangs, with the alternate name appearing on the exterior and interior trim.
The project code is sometimes confused with later Mustang platform codes such as Fox or S197. T-5 specifically belongs to the original development and export history of the first-generation car.