A general multibody model, appropriate for investigating the autorotation of various systems of rigid bodies, is presented. Using the Newton-Euler approach, a generic modular matrix form of the equations of motion is obtained. The general nature of this detailed, nonlinear model allows the description of a large variety of autorotating systems. The calculations of the aerodynamic loads that act on the blades include the use of empirical data combined with an extended blade element/momentum analysis. The model is first validated by comparing its results with analytical results for simple cases. Then the use of the model to investigate the autorotation of a rotor model in a wind tunnel is presented. Good agreement between the experimental and theoretical results is shown.