The Lanchester submachine gun, or Lanchester Mk1, is a historical British firearm that played a crucial role in World War II. Designed by George Lanchester, it was intended to be a cost-effective alternative to the Sten gun for British forces.

Production of the Lanchester began in 1941 at the Sterling Engineering Company in Dagenham, England. It was produced in relatively limited numbers compared to other submachine guns of the era, with approximately 50,000 units manufactured during the war. The production numbers were modest due to the gun's slightly more complex design and the availability of other submachine gun models.

One of the distinctive features of the Lanchester submachine gun was its sturdy and robust construction. It featured a machined steel receiver and barrel, providing durability and reliability on the battlefield.

The Lanchester used a 50-round stick magazine, which was inserted horizontally into the left side of the receiver. This unique magazine design contributed to a more balanced weight distribution for the weapon. This weapon was produced in two versions, Mk.1 and Mk.1*. The Mk.1* was a simplified version of the original Mk.1, which omitted the fire mode selector (full automatic only) and used simplified sights.

The submachine gun's cyclic rate of fire was approximately 500 rounds per minute, which allowed for more controlled bursts and accurate shooting. Its blowback operation, combined with the lower cyclic rate, made it easier for the operator to manage recoil, especially during sustained fire.

The Lanchester submachine gun primarily saw service with the Royal Navy and the British Army's Special Operations Executive (SOE) during World War II. It was used in various theaters of the war, including Europe, North Africa, and the Pacific. After the war, the Lanchester gradually fell out of military use, replaced by newer and more modern submachine gun designs. However, its historical significance, unique features, and reputation for reliability have made it a sought-after collector's item and a piece of firearms history cherished by enthusiasts.