The Rolls-Royce RB.141 Medway was a large low-bypass turbofan engine designed, manufactured and tested in prototype form by Rolls-Royce in the early-1960s. The project was cancelled due to changes in market requirements that also led to the development and production of the smaller but similar Rolls-Royce Spey, and the cancellation of the Armstrong Whitworth AW.681 military transport aircraft project.