The Clerget 9B is a nine-cylinder rotary aircraft engine of the World War I era designed by Pierre Clerget.

Manufactured in both France and Great Britain (Gwynnes Limited), it was used on such aircraft as the Sopwith Camel.

1,300 produced by Ruston Proctor & Co Ltd of Lincoln (1915) 140 hp (104 kW).

Extended stroke 172 mm (6.75 in) version, increasing capacity to 17.5 L (1,066.5 cu in).

The Shuttleworth Collection based at Old Warden Aerodrome, UK, operate an airworthy late production Sopwith Triplane (G-BOCK)[4] fitted with an original 9B as well as an airworthy late production Sopwith Camel (G-BZSC)[5] fitted with an original long-stroke 9Bf.