A torsional vibration is a vibration that occurs in shaft installations, in which a mass due to its inertia, vibrates along the centerline of the shaft or shaft. Torsional vibration can be very dangerous and cause serious damage, such as fatigue in shafts, fretting in splines or keyways, failure of elastic couplings, and damage to gears and clutches.

Furthermore, torsional vibrations can cause disturbance in the proper operation of regulators or governing systems. The danger of torsional vibrations also lies in the fact that torsional vibrations need not result in discomfort to operators or crew until it is too late.