David Keith Duckworth was an English mechanical engineer. He is most famous for designing the Cosworth DFV engine, an engine that revolutionised the sport of Formula One.

The DFV is an internal combustion engine that was originally produced by Cosworth for Formula One motor racing. The name is an abbreviation of Double Four Valve, the engine being a V8 development of the earlier four-cylinder FVA, which had four valves per cylinder.