Sir Hiram Maxim developed a prototype version of the Maxim gun chambered for 7.63×25mm Mauser in about 1896; technically, this can be claimed to be the very first submachine gun, although it was designed to be fired from a mount rather than from the shoulder. Therefore, this gun is perhaps better described as a "heavy submachine gun", as it had all of the typical characteristics of a machine gun, but was chambered for a pistol cartridge.
The Italian Villar Perosa twin-barreled submachine gun was developed in 1914, and was originally designed as a miniature machine gun for support roles. It featured a bipod and spade grips, and was fielded as a crew-served weapon. The Villar Perosa was later adapted into an infantry carbine, the Beretta M1918, which was more akin to a conventional submachine gun. Also during World War I, the Austro-Hungarian Standschütze Hellriegel was prototyped; this was a machine gun chambered for 9mm Steyr rounds. It was fed by a drum magazine with a flexible connector and had a water cooling jacket.
In 1943, Aimo Lahti developed the AL-43, a variant of the Suomi SMG but intended as a light machine gun chambered in a more powerful 9x35mm round (later in 7.62x35mm) which made it ballistically comparable to the StG-44. It came with a bipod and was a large heavy weapon for a submachine gun.
The Czech ZK 383 was a submachine gun that was very large and heavy, and required a bipod to fire effectively. It has a slow rate of fire and could be used as a fairly accurate light support weapon. It saw quite widespread military usage, from about 1938 - 1970.