The Plymouth GTX was first introduced by Chrysler Corporation in 1967 as the Plymouth Belvedere GTX. It was intended to be a muscle car for gentlemen. The Plymouth GTX differentiated itself from the Belvedere because it had a rear fascia, a special grille, mock hood scoops, racing car stripes and fuel filler cap made of chrome. The car also had a standard heavy-duty suspension system and "Super Commando 440" V8 engine. The GTX was a superb blend of performance and style.

The GTX was given a fresh look for the 1968 model after being in production for one year. The 1967 car was more boxlike and this was replaced with an hourglass body. The car retained its high performance 440 cubic-inch engine and automatic transmission was a standard feature. The car came in two models: a 2-door hardtop and a 2-door convertible. Chrysler's new car model, the Road Runner, was also based on the Belvedere but it had less insulation than the GTX which reduced its weight. This also helped give it better track times and kept its price lower than the GTX.

In 1969, the GTXs convertible sales were hurt when the Road Runner also became available as a convertible. Chrysler Corporation decided to make 1969 the last year that the convertible model was available in the GTX. There were only 701 Plymouth GTX convertibles made in 1969. During this same year, the GTX was given lower body black paint as a standard. This had replaced the dual horizontal stripes of the 1968 model.

In 1970, the GTX was given a minor body redesign. The car received a new grille and taillights. Sales still suffered since the car did not look very much different from the Road Runner. The lines of the car were smoothed and a new hood featuring a "power bulge" was introduced. The car was completely redesigned in 1971, but this proved to be its last year of production. Insurance rates on muscle cars had risen considerably and sales for the car were low. In 1971, Chrysler Corporation produced less than 3000 units. Several of the components of the GTX became a package option for the Road Runner from 1972 to 1974.