The Pontiac GTO was built by the Pontiac Division of General Motors from 1964 to 1974. It was a muscle car classic of the 1960s and 1970s. Although there were earlier muscle cars,[ the Pontiac GTO is considered by some to have started the trend, with all four domestic automakers offering a variety of competing models.

Pontiac\'s intermediate line was restyled for 1966, gaining more curvaceous styling.. The tail light featured a louvered cover, only seen on the GTO. Overall length grew, to 206.4 in, on a 115 in wheelbase, and width expanded to 74.4 in. 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. An automotive industry first, plastic front grilles replaced the pot metal and aluminum versions seen on earlier years.

Engine choices remained the same as the previous year. Sales increased to 96,946, the highest production figure for all GTO years. Although Pontiac had strenuously promoted the GTO in advertising as the "GTO Tiger," it had become known in the youth market as the "Goat."