John B. Heywood is a British mechanical engineer known for his work on automotive engine research, for authoring a number of field-defining textbooks on the internal combustion engine, and as the director of the Sloan Automotive Lab at the Massachusetts Institute of Technology (MIT).
Heywood was elected a member of the National Academy of Engineering in 1998 for the prediction of emissions and efficiencies of spark-ignition engines and contributions to national policies on motor emissions.