The M4 Sherman, officially Medium Tank, M4, was the most numerous battle tank used by the United States and some other Western Allies in World War II. In spite of being surpassed by German medium and heavy tanks late in the war, the M4 Sherman proved to be very reliable, cheaper to produce and available in greater numbers. Thousands were distributed through the Lend-Lease program to the British Commonwealth and Soviet Union. The tank was named after the American Civil War General William Tecumseh Sherman by the British.

The M4 Sherman evolved from the interim M3 Medium Tank, which had its main armament in a side sponson mount. The M4 retained much of the previous mechanical design but put the main 75 mm gun in a fully traversing turret. One controversial feature, a one-axis gyro-stabilizer was not precise enough to allow firing when moving but did help keep the reticle on-target, so that when the tank did stop to fire, the gun would be aimed in roughly the right direction. The designers stressed mechanical reliability, ease of production and maintenance, durability, standardization of parts and ammunition in a limited number of variants, and moderate size and weight. These factors, combined with M4 Sherman’s then-superior armor and armament, outclassed German light and medium tanks of 1939–42. The M4 went on to be produced in large numbers. It spearheaded many offensives by the Western Allies after 1942.

When the M4 tank went into combat in North Africa with the British Army at El Alamein in the autumn of 1942, it increased the advantage of Allied armour over German armor and was superior to the lighter German long-barrel 50 mm-gunned Panzer III and the howitzer-like, short-barrel 75 mm-gunned earliest examples of the Panzer IV. For this reason, the US Army believed the M4 would be adequate to win the war, and no pressure was exerted for further tank development. Logistical and transport restrictions, such as limitations imposed by roads, ports, and bridges, also complicated the introduction of a more capable but heavier tank. Tank destroyer battalions using vehicles built on the M4 hull and chassis, but with open-topped turrets and more potent high-velocity guns, also entered widespread use in the American army. Even by 1944, most M4 Shermans kept their dual purpose 75 mm M3. By 1944 and 1945, the M4 was inferior to German heavy tanks but was able to fight on with support from growing numbers of fighter-bombers and artillery pieces.