C40

C40, or variants thereof, may refer to: C40 Cities Climate Leadership Group, a group of 97 cities around the world King's Knight Opening (ECO: C40), a chess opening Yamaha C40, a guitar

==Aircraft== Cierva C.40, a British autogyro designed by G.B.L. Ellis, Otto Reder, and J.A.J Bennett Boeing C-40 Clipper, a military version of the Boeing 737-700C airline transport Lockheed Model 12 Electra Junior (US military designation: C-40), an eight-seat, six-passenger all-metal twin-engine transport aircraft