The Interdynamic MP-9 is a blowback-operated, fully automatic 9 mm caliber firearm, classified by the ATF as a submachine gun.

The MP-9 came from a design that a Swedish company Interdynamic AB of Stockholm had for a cheap submachine gun for military applications.

Interdynamic was unable to drum up any interest among governments, and the subgun never entered production in Sweden.

Interdynamic USA was forced by the ATF to redesign the KG-9 due to its ease of being converted to full auto.

Interdynamic produced a very small quantity of registered MP-9 submachine guns due to lack of demand by the general public.