The M3 Lee, formally Medium Tank, M3, is a World War II U.S. Army version of the M3 medium tank. The turret was built in two versions, one for US requirements and one for British requirements. Prior to the introduction of the M3, the M2 medium tank was the primary medium tank of the U.S. Army. However, the accomplishments of the German Panzer IIIs and Panzer IVs in the French campaign during World War II prompted the U.S. Army to immediately request a new medium tank armed with a 75 mm gun in a turret in response to the new threats. The design began in July 1940, and the M3 medium tank commenced production in late 1940, in response to the United Kingdom's pressing demand for 3,650 medium tanks. The concept was a desperate attempt to get medium tanks built as soon as possible. The M3 medium was designed from the start to be an interim design with a 75 mm gun; hence, it was withdrawn from action in most theatres as soon as the M4 Sherman tanks became available in substantial numbers.

Introduced in Update 1.45 "Steel Generals", the M3 Lee had significant firepower and good armour compared to the previous M2 medium tank, but it had serious drawbacks in its overall design, including a high silhouette, an outdated sponson mounting of the main 75 mm gun resulting in a limited firing arc, riveted construction, and poor off-road performance. Overall, it is a very unusual tank for most players and will require certain coordination to be used effectively.