The TVR Speed Six is the normally aspirated straight-6 engine manufactured by TVR and used in several of their cars including the TVR Tuscan, TVR Cerbera, TVR Tamora, TVR T350 and TVR Sagaris. The engine was produced in two different displacements: 3.6, and 4.0. The two versions use the same piston size but different stroke lengths depending on the power needed for the application.

The heads on all versions of the engines are twin-cam 24-valve, with finger follower valve actuation. There is one throttle and injector per cylinder (throttle body EFI), as well as equal length tubular exhaust manifolds. In addition, the engine is canted 30 degrees to the left and the dry sump lubrication system enables the engine to be mounted lower in the vehicle chassis.