The Cooper T81 was one of the last Formula One racing cars produced by the Cooper Car Company. It was designed ahead of the 1966 World Championship season to operate within the new 3 litre engine regulations that came into effect that year. In place of the 1.5-litre Coventry Climax used under the previous formula, the T81 was powered by Maserati Tipo 9 2.5-litre V12 engines which had been bored out to 3.0-litres. These were supplied by the Chipstead Group, Maserati's UK distributors, who had taken control of Cooper the previous April.

In many ways the car was a typical example of its time, with a rear engine, front radiator, inboard front suspension and a monocoque chassis. In fact the car was Cooper's first monocoque chassis, although by this time such an arrangement had already become standard in Formula 1, having been pioneered by the Lotus 25 four years earlier. Five examples had been built in time for T81's first race, the non-championship BRDC International Trophy at Silverstone on May 14th. Cooper's two works drivers were Richie Ginther and Jochen Rindt, Rob Walker entered a car for Jo Siffert, and Jo Bonnier and Guy Ligier each entered their own cars.

But while the shortage of competitive 3.0 litre F1 machinery at the start of 1966 made the T81 popular, there were suggestions that Cooper were overstretching themselves and that as a result the preparation of the cars was suffering. However, John Surtees, who had replaced Ginther after walking out on Ferrari, took the car's first win in the final race of the 1966 season in Mexico, and in turn Surtees's replacement, Pedro Rodríguez, won the very next race, the 1967 season opener in South Africa. A T81B variant was first raced by Rindt at the 1967 Monaco Grand Prix.

The T81's last race came at the start of the 1968 season in South Africa in the hands of privateers Siffert and Bonnier, as by this time the works team had moved on to the T86 chassis. As it happened, Cooper folded at the end of the 1968 season, making the T81 the last Cooper to win a World Championship Grand Prix.

In all the T81 (and T81B) was entered a total of 85 times in its 21 race lifespan, achieving 2 wins, 1 pole position, 6 podiums, and 23 points finishes, earning 74 points in total.