The Cooper T40 was a Formula 1 car built by the Cooper Car Company and entered in the 1955 Formula 1 season. Designed by Owen Maddock and Jack Brabham, it allowed the latter to make his debut in the discipline of motorsport at the Grand Prix of Great Britain.
In its only appearance in the World Championship, the Cooper T40 only allowed Jack Brabham to qualify twenty-fifth. Brabham did not leave the bottom of the pack and had to retire due to a clutch failure. The Cooper T40 was also committed to three non-championship races around the world. At the London Trophy, at the Crystal Palace circuit, it did not make the start of the race because of a mechanical problem and at the race for the Daily Record Trophy, Brabham finished fourth.