Recent advances in active safety systems provide new opportunities to handle rollover problems more efficiently. This paper presents a Model Predictive Control (MPC) strategy for rollover prevention through active front steering. A new Rollover Index (RI) and a specified vehicle model are proposed to realise an effective rollover prevention approach. The new RI is represented by vehicle parameters and state variables so that it can be readily incorporated into the MPC objective function. Using a barrier cost function, the proposed MPC controller limits vehicle maneuvers within a safe region of rollover without sacrificing vehicle maneuverability under normal conditions. The roll dynamics, the tire nonlinearity, the lateral load transfer, and the road bank are considered for vehicle modelling to provide appropriate actions at the threshold of a rollover. An affine tire model is used to handle tire nonlinearity in the MPC structure. A high-fidelity CarSim model for an SUV is employed to evaluate the proposed RI and the MPC controller. Simulation results show the reliability of the proposed RI and the effectiveness of the proposed rollover prevention controller for different rollover situations.