The Sterling S11 was designed in 1970 by Sterling's chief designer, Frank Waters, as a cheaper alternative to the Sterling Mk.IV, however there was not enough interest in the design to justify a full production run. Only one prototype was made.
The S11 was a basic blowback design similar to the Sterling Mk.IV, but heavily simplified to reduce the cost of production. The body was largely made from stamped steel pressings and the cocking slot ran along the top. However, it retained some of the features of the Mk.IV, such as the left-hand magazine feed and the collapsible buttstock. The S11 was designed with bayonet fittings for the No.5 Mk.1 and L1A3 bayonets.