The GTO was the brainchild of Pontiac engineer Russell Gee, an engine specialist; Bill Collins, a chassis engineer; and Pontiac chief engineer John DeLorean. In early 1963, General Motors' management issued an edict banning divisions from involvement in auto racing. At the time, Pontiac's advertising and marketing approach was heavily based on performance, and racing was an important component of that strategy. With GM's ban on factory-sponsored racing, Pontiac's young, visionary management turned its attention to emphasizing street performance.
The name, which was DeLorean's idea, was inspired by the Ferrari 250 GTO, the successful race car. It is an Italian abbreviation for Gran Turismo Omologato, ("Grand Tourer Homologated") which means officially certified for racing in the Grand tourer class. The name drew protest from enthusiasts, who considered it close to sacrilege.
The GTO was basically a violation of GM policy limiting the A-body intermediate line to a maximum engine displacement of 330 cu in (5.4 L). Since the GTO was an option package and not standard equipment, it could be considered to fall into a loophole in the policy. Pontiac General Manager Elliot "Pete" Estes approved the new model, although sales manager Frank Bridge, who did not believe it would find a market, insisted on limiting initial production to no more than 5,000 cars.
The first Pontiac GTO was an option package for the Pontiac Tempest, available with the two-door coupe, hardtop coupe, and convertible body styles. The US$296, package included a 389 cu in (6.4 L) V8 rated at 325 bhp (242 kW) at 4800 rpm) with a single Carter AFB four-barrel carburetor and dual exhaust, chromed valve covers and air cleaner, 7-blade clutch fan, a floor-shifted three-speed manual transmission with Hurst shifter, stiffer springs, larger diameter front sway bar, wider wheels with 7.50 × 14 redline tires, hood scoops, and GTO badges. Optional equipment included a four-speed manual, Super Turbine 300 two-speed automatic transmission, a more powerful "Tri-Power" carburation rated at 348 bhp (260 kW), metallic drum brake linings, limited slip differential, heavy-duty cooling, ride and handling package, and the usual array of power and convenience accessories. With every available option, the GTO cost about US$ 4,500 and weighed around 3,500 lb (1,600 kg). A tachometer was optional, and was placed in the far right dial on the dash.
The Tempest line, including the GTO, was restyled for the 1965 model year, adding 3.1 inches (79 mm) to the overall length while retaining the same wheelbase and interior dimensions. It had Pontiac's characteristic vertically stacked quad headlights. Overall weight increased about 100 lb (45 kg). The brake lining area increased nearly 15%. Heavy-duty shocks were standard, as was a front antisway bar. The dashboard design was changed, and an optional rally gauge cluster ($86.08) added a more legible tachometer and oil pressure gauge.
Pontiac's intermediate line was restyled again for 1966, gaining more curvaceous styling with kicked-up rear fender lines for a "Coke-bottle" look, and a slightly "tunneled" backlight. The tail light featured a rare louvered cover, only seen on the GTO. Overall length grew only fractionally, to 206.4 in (5,243 mm), still on a 115 in (2,921 mm) wheelbase, while width expanded to 74.4 in (1,890 mm). Rear track increased one inch (2.5 cm). Overall weight remained about the same. The GTO became a separate model series, rather than an optional performance package, with unique grille and tail lights, available as a pillared sports coupe, a hardtop (without B-pillars), or a convertible. Also an automotive industry first, plastic front grilles replaced the pot metal and aluminum versions seen on earlier years. New Strato bucket seats were introduced with higher and thinner seat backs and contoured cushions for added comfort and adjustable headrests were introduced as a new option. The instrument panel was redesigned and more integrated than in previous years with the ignition switch moved from the far left of the dash to the right of the steering wheel. Four pod instruments continued, and the GTO's dash was highlighted by walnut veneer trim.
The GTO underwent a few styling changes in 1967. The louver-covered tail lights were replaced with eight tail lights, four on each side. Rally II wheels with colored lug nuts were also available in 1967. The GTO emblems located on the rear part of the fenders were moved to the chrome rocker panels. Also the grill was changed from a purely split grill, to one that shared some chrome.
The 1967 GTO came in three body styles:
- Hardtop - 65,176 produced
- Convertible - 9,517 produced
- Sports Coupe - 7,029 produced
The 1969 model did not have the vent windows, had a slight grille and taillight revision, moved the ignition key from the dashboard to the steering column (which locked the steering wheel when the key was removed, a Federal requirement installed one year ahead of schedule), and the gauge faces changed from steel blue to black. In addition, the rear quarter-panel mounted side marker lamps changed from a red lens shaped like the Pontiac "V" crest to one shaped like the broad GTO badge. Front outboard headrests were made standard equipment on all GTOs built after January 1, 1969.

The GTO appeared in the early 21st century as a Vauxhall Monaro. But, eventually, the product was discountinued. Rumors say that the 21st Century GTO triggered the launch of the 21st century muscle cars.