The Welgun was a prototype submachine gun developed by the British irregular warfare organisation, the Special Operations Executive.

When issuing arms to resistance fighters throughout Europe, SOE favoured short-range, rapid fire, cost effective weapons which required little training to use, or maintenance in the field.

Early marks were notoriously unreliable and prone to accidental discharges, and some were so badly manufactured that they were issued to resistance fighters with "burrs" in the barrel or working parts which might even cause the weapon to explode when fired.

In early 1943, Sir Charles Hambro, the Director of the SOE, sought permission to have the weapon put into large-scale production.

The Welgun was less reliable in poor operating conditions such as mud or dust, because the first models had been made with too close tolerances.

When this was folded to lie over the barrel and body of the gun, the overall length of the weapon was a little over 16 inches, allowing easy carriage and concealment.