The Cierva W.9 was a British 1940s experimental helicopter with a three-blade tilting-hub controlled main rotor, and torque compensation achieved using a jet of air discharged from the rear port side of the fuselage.

In 1943, primary investor G & J Weir Ltd. revived the moribund Cierva Autogiro Company to develop an experimental helicopter to Air Ministry Specification E.16/43.

It was damaged during ground-running due to incorrect control phasing arising from a high order of pitch-flap coupling, and did not start test flying until 1945.

The most visible characteristic of the W.9 was torque compensation and directional control by using blown air rather than a tail rotor.

Of more importance, however, was the shaft-driven hydraulically-actuated rotor hub with rotational speed variation to give automatic collective pitch control.