This paper presents a realistic, nonlinear numerical open-source benchmark model for Wave Energy Converters (WECs) to facilitate the effective comparison of WEC control strategies. The model represents a point absorber WEC, and was developed in cooperation with CorPower Ocean to obtain a realistic control problem (COERbuoy1), constituting real device characteristics. At the same time, the model is sufficiently representative of the broad class of point absorbers to allow universal findings. The hydrodynamic forces are calculated using instantaneous linearisation of the hydrodynamic parameters for body-exact wave-body interactions in two degrees of freedom. Additionally, the model includes nonlinear effects such as viscous drag, static and dynamic friction, a power take-off using an electric generator with saturation effects, and a nonlinear spring opposing the hydrostatic stiffness. The benchmark problem consists of three stages: Testing the control performance in (1) regular and (2) irregular waves and by (3) using small modifications in the model to challenge the controller’s ability to handle modelling errors. The benchmark scoring system evaluates the controller on the basis of the absorbed power and adherence to motion and power constraints. The system is tested with an illustrative constant damping power-take-off, showing reasonably good results in power absorption for low period cases, but poor results for long wave periods.