The tokamak is a torus-shaped machine in which a reactant ionized gas (plasma) is confined using magnetic fields for the purpose of generating energy from nuclear fusion reactions. In order to be commercially competitive, a tokamak needs to operate for long periods of time at high-performance operating points. Those high-performance scenarios are characterized by a steady-state, stable plasma operation, which is closely related to a property of the plasma that is known as the safety factor, q. Therefore, control of the q profile is one of the crucial aspects to the success of tokamaks. Significant research has been carried out by the fusion community to find control algorithms for the q profile. Most of that previous work makes use of approximate linearization and linear control techniques. In the present work, we propose a nonlinear model-based controller for the regulation of the q profile using feedback linearization. This nonlinear control approach may be applicable to a greater range of operating conditions, and may be able to reject larger perturbations than previous linear controllers. The effectiveness of the controller is demonstrated via a simulation study based on a DIII-D scenario.