The Pistolet Mitrailleur Modèle 1939 (lit. Model 39 submachine gun), also known as the Petter Mle 1939, was a French submachine gun that was produced by Société Alsacienne de Constructions Mécaniques (SACM).
Originally designed by Charles G. Petter, the Petter submachine gun was developed by SACM and submitted for French military trials in 1937. The Petter was tested separately from the previous submachine guns investigated by the French Army, as it was submitted too late to be factored into comparative trials. Nonetheless, the Army expressed an interest in the design and ordered 3,000 units for limited adoption as the Mle 1939, alongside the MAS 38. SACM, however, declined the order, as they were already hard-pressed to complete an order of several thousand Mle 1935A pistols and MAS 36 rifles. There was no attempt to put the Petter submachine gun into full production and only 50 pre-production samples were ever made. These existent guns were allegedly pressed into limited service during the German invasion of France in 1940.
The design was revived post-war in the form of the MAS 48 submachine gun.
The Petter submachine gun used a blowback-operated action utilizing an L-shaped bolt, in which much of the bolt's mass lay in a long tubular section over the barrel. The bolt rode on a guide rod and a loose, spring-loaded firing pin was housed inside the bolt face at a tilted angle. The magazine housing was hinged and the magazine could lay horizontally underneath the barrel when not in use. The gun used a fixed wooden stock that could be removed as a single unit.