The T20E3 was a medium tank that was part of the E3 in the series of T20 tanks. It was designed by the US Ordnance Department during the Second World War. It was never produced.
Design of the T20 began in May 1942 and avoided the narrow and high hull forced on the Sherman by its evolution from the M2 and M3 medium tanks, devising a low and sleek hull topped with a new and larger turret. Ordnance was interested in mounting its new Ml 76mm gun in the new design, but lacking any firm battle need from the armored force for such a weapon, it also worked on versions with the existing 75mm gun, including one fed from an automatic loader. The T20E3 pilot was completed by General Motors in July 1943 and introduced the more advanced torsion bar suspension that would later emerge with the final M26 Pershing tank.
There was no particular pressure to push a new design into production, so development of the T20 was leisurely by World War II standards, with the pilots delivered in the spring of 1943. Because of the lack of urgency, a variety of spin-offs appeared, such as the T22, which took the powertrain from the M4A3 Sherman instead of the new rear-mounted torquematic transmission used in the T20. The T23, an even more ambitious alternative, used a General Electric electric transmission.