USA, 1942–1943
Type: Light Tank
Chassis: M3 (modified)
Main Armament: 37 mm M6 gun
Armor: 13–51 mm (riveted or welded)
Technical Manuals: TM 9-731B, TM 9-1726D, TM 9-1726E

The M3A1 was a major refinement of the M3 Stuart, introducing a simplified turret with power traverse, improved periscopes, and removal of the sponson-mounted machine guns.
Standardized in May 1942, it retained the same hull and suspension but featured the low-profile D58101 welded or cast turret, a rotating M6 periscope, and internal radio mounting. A gyroscopically stabilized 37 mm M6 gun became standard, enhancing fire-on-the-move capability. The commander still served as gunner, which remained a key ergonomic limitation. Over 4,400 units were produced before it was succeeded by the M3A3 and M5 series ¹.