Mustang got another major restyling in 1971. They grew in length and got a wider stance. This was the first year of the “big” Mustang.

The simulated air scoops were eliminated and the headlamps moved out to the fenders once more. The Mustang corral returned as a wide chrome strip. The long hood turned up at the windshield to cover the wipers. Recessed door handles replaced the earlier surface mounted handles.

The interior featured standard high-back buckets, a mini console, and an all-new instrumentation layout. Power windows were offered for the first time in 1971.

The 200ci six-cylinder was dropped along with the 428, the Boss 302, and the Boss 429. New engines for 1971 were the Boss 351, the 429, and the Ram Air 429.

The Mach 1 was available with any of the V8 engines. A special honeycomb grille and color keyed urethane front bumper were unique to the Mach 1 model. The chrome hood and fender moldings were replaced with color-keyed trim. "Mach 1" decals were placed on the fenders and deck lid and a special black or argent paint was used on the lower body sides.

New for 1971 was the Boss 351, which replaced the Boss 302, and Boss 429. The Boss 351 featured a 351-4V Cleveland engine and a blacked-out scooped hood with twist type locks and special side stripes. This would be the last year for the Boss models.